Unit 3: Definition, Causes & Preventive measures, Types, Educational Implications, and Management of-

3.1  Intellectual Disability;

3.2  Specific Learning Disabilities;

3.3  Autism Spectrum Disorder;

3.4  Mental Illness, Multiple Disabilities;

3.5  Chronic Neurological conditions and Blood Disorders;












3.1   Intellectual Disability;


There are many definitions of mental retardation, the most comprehensive among them is the one given by the American Association on Mental Retardation (AAMR) 1983 restated till 2004.

The Mental Deficiency Act of 1921 in England considered “ Mental defectiveness as a condition of arrested or in complete development of mind existing before the age of eighteen years, whether arising from inherent causes or induced by disease or injury.

According to American Association on Mental Dediciency (AAMD), 1956....

   “Mental retardation refers to sub-average general intellectual functioning, which originates during the developmental period and is associated with impairments in adaptive behaviour.”

This definition refers to sub-average intelligence, which is explained as one SD below the mean (approximately 85 and below 100-15=85). This developmental period was described as birth to 16years. Using this definition for legal purposes, it was observed that a number of persons who were close to normal (IQ 70 to 85) were receiving support. By incidence too they are more in number and as the severity increases the number of persons affected reduces. As it was not serving the purposes and the right population, the definition was revised in 1973.

AAMR, 1992....

  “Mental retardation refers to substantial limitation in present functioning. It is characterized by significantly sub-average intellectual functioning, existing concurrently and with related limitations in two or more of the applicable adaptive areas: communication, self care, home living, social skills, community use, self direction, health and safety, functional academics, leisure and work. Mental retardation manifest before age 18.”

q Limited Functioning

The first part of this definition establishes mental Retardation as a category of concern for people whose current levels of functioning are limted. Mental Retardation is difficulty in learning and performing certain daily life skills as a esult of substantial limitations in conceptual, practical and social intelligence.

q Intellectual Functioning

The second part of the definition “significantly sub- average intellectual functioning” usually translated as a score of 70 to 75 or below on one or more individually administered general intelligence tests. Tests scores and other information are reviewed and evaluated by teams of professionals as a part of the process of diagnosing Mental Retardation.

q Adaptive Skills

The third part that the individual must also demonstrate lilted adaptive skills in key areas- is an important part od=f the definition. First, adaptive skill limitations must occur at the same time as intellectual limitations; intellectual functionong alone is insufficient basis for a diagnosis of mental retardation. Second, more than one area of adaptive skills must be limited to reduce the chnces of making a mistake in diagnosing Mental Retardation.

AAMR, 2002...

“Mental retardation is a disability characterized by significant limitations both in intellectual functioning and in adaptive behavior as expressed in conceptual, social, and practical adaptive skills.  This disability originates before age 18.”




Ø   130+        Very Superior (Gifted)

Ø   120-129   Superior

Ø   110-119   High Average

Ø   90-119     Average

Ø   80-89       Low Average

Ø   70-79       Borderline

Ø   69 and below   Mental impairment

q AAMD/AAMR Classification Systems

Heber (1961)     

           Borderline   68-84

           Mild             52-67

           Moderate    36-51

           Severe        20-35

           Profound     <20

q Profiles of Intellectual Disability


Ø Mild ID Profile

           Minor delays in the preschool period

           Evaluation often only after school entry

           2-3 word sentences used in early primary grades

           Expressive language improvement with time

           Reading/math skills – 1st to 6th grade levels

           Social interests typically age appropriate

           Mental age range of 8-11 years of age

           Persistent low academic skill attainment can limit vocational possibilities


Ø Moderate ID Profile

           More evident and consistent delays in milestones

           At school entry may communicate with single words and gestures

           Functional language is the goal

           School entry self-care skills – 2-3 year range

           By age 14:  basic self-care skills, simple conversations, and cooperative social interactions

           Mental age of 6-8 years of age

           Vocational opportunities limited to unskilled work with direct supervision and assistance


Ø Severe ID Profile

           Identification in infancy to two years

           Often co-occurring with biological anomalies

           Increased risk for motor disorders and epilepsy

           By age 12:  may use 2-3 word phrases

           Mental age typically 4-6 years of age

           As adults assistance typically required for even self-care activities

           Close supervision needed for all vocational tasks


Ø Profound ID Profile

           Identification in infancy

           Marked delays and biological anomalies

           Preschool age range may function as a 1-year-old

           High rate of early mortality

           By age 10:  some walk/acquire some self-care skills with assistance

           Gesture communication

           Recognizes some familiar people

           Mental age range from birth to 4 years of age

           Functional skill acquisition not likely



3.2   Specific Learning Disabilities;


Learning disabilities (LEARNING DISABILITYs) are real. They affect the brain's ability to receive, process, store, respond to and communicate information. LEARNING DISABILITYs are actually a group of disorders, not a single disorder.

Learning disabilities are not the same as intellectual disabilities (formerly known as mental retardation), sensory impairments (vision or hearing) or autism spectrum disorders. People with LEARNING DISABILITY are of average or above-average intelligence but still struggle to acquire skills that impact their performance in school, at home, in the community and in the workplace. Learning disabilities are lifelong, and the sooner they are recognized and identified, the sooner steps can be taken to circumvent or overcome the challenges they present.


‘Learning disability includes the presence of:

• a significantly reduced ability to understand new or complex information, to learn new skills (impaired intelligence), with;

• a reduced ability to cope independently (impaired social functioning);

• which started before adulthood, with a lasting effect on development.


 A condition of arrested or incomplete development of the mind, which is especially characterised by impairment of skills manifested during the developmental period, which contribute to the overall level of intelligence, i.e. cognitive, language, motor and social abilities.


Specific learning disability refers to heterogeneous clusters of disorders that significantly impede the normal progress of academic achievement in 2%-3% of the school population. The lack of progress is exhibited in school performance that remains below expectation for chronological and mental ages, even when provided with high-quality instruction. The primary manifestation of the failure to progress is significant underachievement in a basic skill area (i.e., reading, math, writing) that is not associated with insufficient educational, interpersonal, cultural/familial, and/or sociolinguistic experiences. The primary severe ability-achievement discrepancy is coincident with deficits in linguistic competence (receptive and/or expressive), cognitive functioning (e.g., problem solving, thinking abilities, maturation), neuropsychological processes (e.g., perception, attention, memory), or any combination of such contributing deficits that are presumed to originate from central nervous system dysfunction. The specific learning disability is a discrete condition differentiated from generalized learning failure by average or above (> 90) cognitive ability and a learning skill profile exhibiting significant scatter indicating areas of strength and weakness. The major specific learning disability may be accompanied by secondary learning difficulties that also may be considered when planning the more intensive, individualized special education instruction directed at the primary problem.

Specific types of learning disabilities and related disorders


Area of difficulty

Symptoms include trouble with



Processing language

·       Reading

·       Writing

·       Spelling

Confusing letter names and sounds, difficulties blending sounds into words, slow rate of reading, trouble remembering after reading text


Math skills

·       Computation

·       Remembering math facts

·       Concepts of time and money

Difficulty learning to count by 2s, 3s, 4s, poor mental math skills, problems with spatial directions


Written expression

·       Handwriting

·       Spelling

·       Composition

Illegible handwriting, difficulty organizing ideas for writing


Fine motor skills

·       Coordination

·       Manual dexterity

Trouble with scissors, buttons, drawing

Information Processing Disorders

Auditory Processing Disorder

Interpreting auditory information

·       Language development

·       Reading

Difficulty anticipating how a speaker will end a sentence

Visual Processing Disorder

Interpreting visual information

·       Reading

·       Writing

·       Math

Difficulty distinguishing letters like “h” and “n”

Other Related Disorders

Attention-Deficit/ Hyperactivity Disorder (ADHD)

Concentration and focus

·       Over-activity

·       Distractibility

·       Impulsivity

Can't sit still, loses interest quickly, daydreams



3.3                  Autism Spectrum Disorder;


World Health Organisation (WHO) 2013

       Core symptoms: Mixture of impaired capacity for reciprocal socio-communicative interaction and a restricted, stereotyped repetitive repertoire of interests. Individuals with ASD may have decreased general intellectual ability.

       Neuro-developmental impairments in communication, social interaction and unusual ways of perceiving and processing information hinders daily functioning of people with ASDs and  impede their educational and social attainments.

The Individuals with Disabilities Education Act (IDEA)

       A developmental disability affecting verbal and non-verbal communication and social interaction,(Age<3).

        Engagement in repetitive activities and stereotyped movements, resistance to environmental change or change in daily routines, and unusual responses to sensory experiences.

Rehabilitation Council of India (RCI)

       Autism is one of five developmental disorders included under the umbrella of the Pervasive Developmental Disorders.

       Autism is characterized by deficits in social interaction and communication, and unusual and repetitive behaviour. autism manifests at birth or within the first two-and-a-half years of life.

The Americans with Disabilities Act of 1990 (ADA)

       Autism is defined as a developmental disability significantly affecting verbal and non- verbal communication and social interaction, generally (< age 3), which adversely affects a child's educational performance

Types of ASD

The most recent and updated version of the Diagnostic and Statistical Manual of Mental Disorders version 5 (DSM -5) of American Psychiatric Association has just a single category for the diagnosis of an autistic disorder – autism spectrum disorders, which include the following disorders that were previously discussed separately:

       Autism or Autistic Disorder: Children who seem to have met most of the rigid criteria of a diagnosis of Autism are said to have Autism or Autistic Disorder. They have moderate to severe impairments in Social and Language skills, possess Repetitive Behaviors and Restricted Interests. Often the children and individuals with Autistic Disorder also have mental retardation and seizures.

       Asperger’s Syndrome: AS, is the mildest form of Autism. It is found to have affected boys three times more in comparison with girls.

The most common symptoms of Asperger Syndrome are the children affected become excessively interested in a single subject or topic. They tend to find out and learn everything about their preferred subject and talk about it all the time. As compared with other form of Autism, children with Asperger have extremely good vocabulary however their social skills are markedly impaired and they are often awkward and uncoordinated.

It is also found that the children with Asperger’s Syndrome very often have normal or above normal IQ (Intelligence Quotient). As a result, many doctors address it as High-Functioning Autism. As children with AS enter into Childhood, they are at a high risk of developing Anxiety and Depression.

       PDD-NOS (Pervasive Development Disorder, Not Otherwise Specified) : PDD-NOS is a little complex syndrome to diagnose amongst children on the Autism Spectrum. Commonly children & individuals whose behavioral symptoms are more severe than Asperger’s Syndrome but less severe than Autistic Disorder are diagnosed as PDD-NOS.

No two children/individuals with PDD-NOS exhibit similar symptoms. This makes generalizing the disorder rather more complex. Commonly, children with PDD-NOS exhibit following symptoms:

Impaired social communication/interaction (similar to Autistic Disorder)

Better language/communication skills as compared to children with Autistic Disorder however these skills are not as good as of children with Asperger’s Syndrome

Lesser sensory dysfunction as a result fewer repetitive behaviors

       Rett Syndrome : Rett Syndrome is severe form of Autism and it mostly occurs in girls. It is mostly caused by a genetic mutation wherein the mutation occurs randomly and has no inherited significance. It is a rare syndrome affecting about one in 10,000-15,000 girls.

In this syndrome, girls aging between 6 to 18 months of age regress marginally and lose linguistic and social skills. They habitually wring hands and develop coordination problems. Head growth slows down significantly and by the age of two their head appears to be far below normal. The treatment of Rett Syndrome focuses mostly on physical therapy and speech therapy to improve function.

       Child Disintegrative Disorder : It is the least common and most severe form of Autism Spectrum Disorder. In CDD, the child rapidly loses multiple areas of function between the ages of 2 to 4 years of age. This regression takes place in social skills, linguistic skills as well as in intellectual abilities.

Very often the child develops a seizure disorder. The children with CDD – Childhood Disintegrative Disorder are severely impaired and don’t recover their lost function.

The number of children affecting CDD is lesser than 2 children per 100,000 children with Autism Spectrum Disorder. Boys are more commonly affected by CDD than girls.


3.4                  Mental Illness,

The WHO stress that mental health is “more than just the absence of mental disorders or disabilities.” Peak mental health is about not only avoiding active conditions but also looking after ongoing wellness and happiness.

They also emphasize that preserving and restoring mental health is crucial on an individual basis, as well as throughout different communities and societies the world over.

According to WHO-

Mental disorders comprise a broad range of problems, with different symptoms. However, they are generally characterized by some combination of abnormal thoughts, emotions, behaviour and relationships with others. Examples are schizophrenia, depression, intellectual disabilities and disorders due to drug abuse. Most of these disorders can be successfully treated.

There are many different conditions that are recognized as mental illnesses. The more common types include:

·       Anxiety disorders: People with anxiety disorders respond to certain objects or situations with fear and dread, as well as with physical signs of anxiety or panic, such as a rapid heartbeat and sweating. An anxiety disorder is diagnosed if the person's response is not appropriate for the situation, if the person cannot control the response, or if the anxiety interferes with normal functioning. Anxiety disorders include generalized anxiety disorder, panic disorder, social anxiety disorder, and specific phobias.

·       Mood disorders: These disorders, also called affective disorders, involve persistent feelings of sadness or periods of feeling overly happy, or fluctuations from extreme happiness to extreme sadness. The most common mood disorders are depression, bipolar disorder, and cyclothymic disorder.

·       Psychotic disorders: Psychotic disorders involve distorted awareness and thinking. Two of the most common symptoms of psychotic disorders are hallucinations -- the experience of images or sounds that are not real, such as hearing voices -- and delusions, which are false fixed beliefs that the ill person accepts as true, despite evidence to the contrary. Schizophrenia is an example of a psychotic disorder.

·       Eating disorders: Eating disorders involve extreme emotions, attitudes, and behaviors involving weight and food. Anorexia nervosa, bulimia nervosa, and binge eating disorder are the most common eating disorders.

·       Impulse control and addiction disorders: People with impulse control disorders are unable to resist urges, or impulses, to perform acts that could be harmful to themselves or others. Pyromania (starting fires), kleptomania (stealing), and compulsive gambling are examples of impulse control disorders. Alcohol and drug are common objects of addictions. Often, people with these disorders become so involved with the objects of their addiction that they begin to ignore responsibilities and relationships.

·       Personality disorders: People with personality disorders have extreme and inflexible personality traits that are distressing to the person and/or cause problems in work, school, or social relationships. In addition, the person's patterns of thinking and behavior significantly differ from the expectations of society and are so rigid that they interfere with the person's normal functioning. Examples include antisocial personality disorder, obsessive-compulsive personality disorder, and paranoid personality disorder.

·       Obsessive-compulsive disorder (OCD): People with OCD are plagued by constant thoughts or fears that cause them to perform certain rituals or routines. The disturbing thoughts are called obsessions, and the rituals are called compulsions. An example is a person with an unreasonable fear of germs who constantly washes his or her hands.

·       Post-traumatic stress disorder (PTSD): PTSD is a condition that can develop following a traumatic and/or terrifying event, such as a sexual or physical assault, the unexpected death of a loved one, or a natural disaster. People with PTSD often have lasting and frightening thoughts and memories of the event, and tend to be emotionally numb.


3.5   Chronic Neurological conditions and Blood Disorders;


A lot of people feel confused about which diseases are covered under the umbrella term Chronic Neurological Conditions. India’s RPWD Act 2016 mentions Chronic Neurological Conditions as one of the recognized disabilities. In order to provide a meaning or definition of these conditions, the guidelines give examples of Multiple Sclerosis and Parkinson’s disease.

Definition and Meaning of Chronic Neurological Conditions

The 4th July 2018 notification of the Ministry of Social Justice and Empowerment give definition as below:

Chronic neurological conditions, such as—
(i) “multiple sclerosis” means an inflammatory, nervous system disease in which the myelin sheaths around the axons of nerve cells of the brain and spinal cord are damaged, leading to demyelination and affecting the ability of nerve cells in the brain and spinal cord to communicate with each other;
(ii) “Parkinson’s disease” means a progressive disease of the nervous system marked by tremor, muscular rigidity, and slow, imprecise movement, chiefly affecting middle-aged and elderly people associated with degeneration of the basal ganglia of the brain and a deficiency of the neurotransmitter dopamine.

But MS and PD have been cited only as examples.

Neurological disorders are diseases of the central and peripheral nervous system. In other words, the brain, spinal cord, cranial nerves, peripheral nerves, nerve roots, autonomic nervous system, neuromuscular junction, and muscles. These disorders include epilepsy, Alzheimer disease and other dementias, cerebrovascular diseases including stroke, migraine and other headache disorders, multiple sclerosis, Parkinson's disease, neuroinfections, brain tumours, traumatic disorders of the nervous system due to head trauma, and neurological disorders as a result of malnutrition.

Many bacterial (i.e. Mycobacterial tuberculosis, Neisseria meningitides), viral (i.e. Human Immunodeficiency Virus (HIV), Enteroviruses, West Nile Virus, Zika), fungal (i.e. Cryptococcus, Aspergillus), and parasitic (i.e. malaria, Chagas) infections can affect the nervous system. Neurological symptoms may occur due to the infection itself, or due to an immune response.


There are other conditions that can be categorized under Chronic Neurological Conditions. Some more examples can be:

1.     Alzheimer’s disease and Dementia

2.     Parkinson’s disease

3.     Dystonia

4.     ALS (Lou Gehrig’s disease)

5.     Huntington’s disease

6.     Neuromuscular disease

7.     Multiple sclerosis

8.     Epilepsy

9.     Stroke


Dementia is a deterioration of intellectual function and other cognitive skills that is of sufficient severity to interfere with social or occupational functioning. Of the many diseases that lead to dementia, AD is the most common cause worldwide among people age 65 and older, followed by vascular dementia, mixed dementia consisting of AD plus vascular dementia, and dementia caused by general medical conditions. Although distinguishing AD from other causes of dementia is important, particularly for treatment with acetylcholinesterase inhibitors, the burden from all causes of dementia is similar. Although the discussion in this chapter deals mostly with AD, the role of treatable dementias in developing countries is important as it can reduce the burden of caring in families. In the early stages of Alzheimer's disease, memory loss is mild, but in its late-stage, individuals lose the ability to complete daily tasks, carry on a conversation, and respond to their environment. Alzheimer's disease is the sixth leading cause of death in the United States. Those with Alzheimer's disease live an average of eight years after their symptoms become noticeable. However, depending on age and other health conditions, survival can range from four to 20 years.

Risk and Protective Factors and Survivorship

Three separate genes (APP, PS1, and PS2) are linked to earlyonset, familial AD. Another gene (APO E4) is a risk factor for late-onset, nonfamilial cases (Henderson and Jorm 2000). Other genes have been implicated but not confirmed in large studies. Other risk factors reported in the literature include increasing age, positive family history of dementia, female gender (but this factor is controversial), lower level of education, several medical conditions, and exposure to such environmental factors as organic solvents and aluminum. Protective factors reported in the literature include a higher level of education, a specific gene (APO E2), the intake of antioxidants, and the use of some anti-inflammatory medications. The use of estrogen supplements for women was believed to be a protective factor for AD (Henderson 1997), but a recent study of women taking a combination of estrogen and progesterone showed that these women had twice the risk of developing dementia than women taking a placebo. Studies from developed countries have reported median survival after the onset of dementia symptoms ranging from 5.0 years to 9.3 years (Walsh, Welch, and Larson 1990). In developing countries, the reported median survival was 3.3 years for all demented subjects and 2.7 years for those with AD.


PD is characterized by bradykinesia, resting tremor, cogwheel rigidity, postural reflex impairment, progressive course, and good response to dopaminergic therapy. Other distinct forms of parkinsonism include relatively rare genetic forms and the less common neurodegenerations with multiple system involvement or significant striatal lesions (for example, progressive supranuclear palsy or multiple system atrophy). Parkinsonism secondary to external causes, such as manganese poisoning or carbon monoxide poisoning, although now rare, is referred to as secondary parkinsonism. Because the burden of these diseases to the patient is similar to or greater than that for PD and there is no evidence for addressing these disorders separately, they will not be distinguished here.

Parkinson's signs and symptoms may include:

·       Tremor. A tremor, or shaking, usually begins in a limb, often your hand or fingers. You may a rub your thumb and forefinger back-and-forth, known as a pill-rolling tremor. Your hand may tremor when it's at rest.

·       Slowed movement (bradykinesia). Over time, Parkinson's disease may slow your movement, making simple tasks difficult and time-consuming. Your steps may become shorter when you walk. It may be difficult to get out of a chair. You may drag your feet as you try to walk.

·       Rigid muscles. Muscle stiffness may occur in any part of your body. The stiff muscles can be painful and limit your range of motion.

·       Impaired posture and balance. Your posture may become stooped, or you may have balance problems as a result of Parkinson's disease.

·       Loss of automatic movements. You may have a decreased ability to perform unconscious movements, including blinking, smiling or swinging your arms when you walk.

·       Speech changes. You may speak softly, quickly, slur or hesitate before talking. Your speech may be more of a monotone rather than with the usual inflections.

·       Writing changes. It may become hard to write, and your writing may appear small.

Causes and Risk Factors

The cause of PD is unknown. A specific environmental risk factor has not been identified. Pure genetic forms account for 10 to 15 percent of cases or fewer. Increasing age and male gender are risk factors worldwide. Exposure to toxins, head trauma, frequent infections, diets high in animal fat, and midlife adiposity have been reported to increase PD risk, but none do so consistently. The most consistent association is an inverse association with cigarette smoking and caffeine consumption, suggesting a protective effect.


Epilepsy is a common brain disorder characterized by two or more unprovoked seizures. Seizures are discrete events caused by transient, hypersynchronous, abnormal neuronal activity. Seizures may occur in close temporal association with a variety of acute medical and neurological diseases, such as acute stroke, sepsis, or alcohol withdrawal. However, the vast majority of seizures have no immediate identifiable cause. Epilepsy can be broadly divided into three categories: idiopathic epilepsy (for example primary generalized childhood-onset absence epilepsy), which is thought to have a genetic basis; secondary or symptomatic epilepsy, which is caused by a known central nervous system injury or disorder, such as infection, stroke, traumatic brain injury, or cerebral dysgenesis; and cryptogenic epilepsy, for which there is no clear evidence of an etiological factor. Idiopathic and cryptogenic cases represent approximately 70 percent of epilepsy cases; the remaining 30 percent are symptomatic (secondary). Seizures are the main symptom of epilepsy. Symptoms differ from person to person and according to the type of seizure.

Focal seizures

When seizures appear to result from abnormal activity in just one area of your brain, they're called focal (partial) seizures. These seizures fall into two categories:

·       Focal seizures without loss of consciousness. Once called simple partial seizures, these seizures don't cause a loss of consciousness. They may alter emotions or change the way things look, smell, feel, taste or sound. They may also result in involuntary jerking of a body part, such as an arm or leg, and spontaneous sensory symptoms such as tingling, dizziness and flashing lights.

·       Focal seizures with impaired awareness. Once called complex partial seizures, these seizures involve a change or loss of consciousness or awareness. During a complex partial seizure, you may stare into space and not respond normally to your environment or perform repetitive movements, such as hand rubbing, chewing, swallowing or walking in circles.

Symptoms of focal seizures may be confused with other neurological disorders, such as migraine, narcolepsy or mental illness. A thorough examination and testing are needed to distinguish epilepsy from other disorders.

Generalized seizures

Seizures that appear to involve all areas of the brain are called generalized seizures. Six types of generalized seizures exist.

·       Absence seizures. Absence seizures, previously known as petit mal seizures, often occur in children and are characterized by staring into space or subtle body movements such as eye blinking or lip smacking. These seizures may occur in clusters and cause a brief loss of awareness.

·       Tonic seizures. Tonic seizures cause stiffening of your muscles. These seizures usually affect muscles in your back, arms and legs and may cause you to fall to the ground.

·       Atonic seizures. Atonic seizures, also known as drop seizures, cause a loss of muscle control, which may cause you to suddenly collapse or fall down.

·       Clonic seizures. Clonic seizures are associated with repeated or rhythmic, jerking muscle movements. These seizures usually affect the neck, face and arms.

·       Myoclonic seizures. Myoclonic seizures usually appear as sudden brief jerks or twitches of your arms and legs.

·       Tonic-clonic seizures. Tonic-clonic seizures, previously known as grand mal seizures, are the most dramatic type of epileptic seizure and can cause an abrupt loss of consciousness, body stiffening and shaking, and sometimes loss of bladder control or biting your tongue.

Risk Factors

A reported risk factor for idiopathic (presumed genetic) epilepsy is family history of epilepsy. Reported risk factors for symptomatic epilepsy include prenatal or perinatal causes (obstetric complications, prematurity, low birthweight, neonatal asphyxia). Recent data suggest that the effect of obstetric complications or neonatal asphyxia may have been overemphasized. Prematurity, low birthweight, and neonatal seizures may be independent risk factors as well as markers of underlying disease. Other causes include traumatic brain injuries, central nervous system infections, cerebrovascular disease, brain tumors, and neurodegenerative diseases. Developmental disabilities are not a risk factor for epilepsy in themselves, but they may be associated with seizure disorder.


Multiple sclerosis (MS) is an inflammatory demyelinating condition of the central nervous system (CNS) that is generally considered to be autoimmune in nature. In people with MS, the immune trigger is unknown, but the targets are myelinated CNS tracts. In regions of inflammation, breakdown of the blood–brain barrier occurs and destruction of myelin ensues, with axonal damage, gliosis and the formation of sclerotic plaques. Plaques (MS lesions) may form in the CNS white matter in any location (and also in grey matter); thus, clinical presentations may be diverse. Continuing lesion formation in MS often leads to physical disability and, not infrequently, to cognitive decline. Multiple sclerosis signs and symptoms may differ greatly from person to person and over the course of the disease depending on the location of affected nerve fibers. Symptoms often affect movement, such as:

·       Numbness or weakness in one or more limbs that typically occurs on one side of your body at a time, or your legs and trunk

·       Electric-shock sensations that occur with certain neck movements, especially bending the neck forward (Lhermitte sign)

·       Tremor, lack of coordination or unsteady gait

Vision problems are also common, including:

·       Partial or complete loss of vision, usually in one eye at a time, often with pain during eye movement

·       Prolonged double vision

·       Blurry vision

Multiple sclerosis symptoms may also include:

·       Slurred speech

·       Fatigue

·       Dizziness

·       Tingling or pain in parts of your body

·       Problems with sexual, bowel and bladder function

Types of MS

There are four types of MS:

Clinically isolated syndrome (CIS): This is a single, first episode, with symptoms lasting at least 24 hours. If another episode occurs at a later date, a doctor will diagnose relapse-remitting MS.

Relapse-remitting MS (RRMS): This is the most common form, affecting around 85% of people with MS. RRMS involves episodes of new or increasing symptoms, followed by periods of remission, during which symptoms go away partially or totally.

Primary progressive MS (PPMS): Symptoms worsen progressively, without early relapses or remissions. Some people may experience times of stability and periods when symptoms worsen and then get better. Around 15% of people with MS have PPMS.

Secondary progressive MS (SPMS): At first, people will experience episodes of relapse and remission, but then the disease will start to progress steadily.

Risk Factors

The worldwide distribution of MS can be only an indirect refl ection of its cause, implicating some environmental factor that varies with latitude, and can be interpreted in at least three different ways in the search for clues to a specifi c etiology. First, an environmental risk factor may be more common in temperate than tropical climates. Second, such a factor may be more common in tropical climates, where it is acquired at an earlier age and consequently has less impact. Third, this factor may be equally common in all regions, but the chance of its acquisition or of the manifestation of symptoms is either increased by some enhancing factor present in temperate climates or reduced by a protective factor present in tropical areas. Among those factors that have been most closely scrutinized are:

·      infections, including a number of viral infections such as measles and Epstein–Barr virus;

·      climate and solar conditions;

·      living conditions;

·      diet and trace elements.

It is now generally accepted that the etiology of MS involves some interplay of genetic and environmental factors. Evidence of racial or ethnic resistance, the increased risk among MS family members, and elevated monozygotic twin concordance rate all favour a genetic contribution to acquisition of the disease. The studies from which this evidence is derived, however, also indicate that heredity cannot entirely explain the occurrence of MS. This is underlined by the fact that no population-based study of monozygotic twins has found a concordance rate in excess of 30%. Some environmental factor, such as a virus or toxin, must still play a role.


Dystonia is a very complex, highly variable neurological movement disorder characterized by involuntary muscle contractions. Dystonia results from abnormal functioning of the basal ganglia, a deep part of the brain which helps control coordination of movement. These regions of the brain control the speed and fluidity of movement and prevent unwanted movements. Patients with dystonia may experience uncontrollable twisting, repetitive movements or abnormal postures and positions. These can affect any part of the body, including the arms, legs, trunk, face and vocal cords.

Depending on the part of the body affected, dystonia can seriously impact daily functions. For example, if neck muscles are affected, a patient may have difficulty chewing and swallowing. Though not life-threatening, the involuntary nature of the disorder may be embarrassing, causing emotional distress or depression in some individuals. There are a number of local support groups throughout the United States that can help address some of these issues, but patients may need to be treated separately for mental health issues caused by the challenges of coping with this disorder.


ALS, or amyotrophic lateral sclerosis, is a progressive neurodegenerative disease that affects nerve cells in the brain and the spinal cord. A-myo-trophic comes from the Greek language. "A" means no. "Myo" refers to muscle, and "Trophic" means nourishment – "No muscle nourishment." When a muscle has no nourishment, it "atrophies" or wastes away. "Lateral" identifies the areas in a person's spinal cord where portions of the nerve cells that signal and control the muscles are located. As this area degenerates, it leads to scarring or hardening ("sclerosis") in the region.

Motor neurons reach from the brain to the spinal cord and from the spinal cord to the muscles throughout the body. The progressive degeneration of the motor neurons in ALS eventually leads to their demise. When the motor neurons die, the ability of the brain to initiate and control muscle movement is lost. With voluntary muscle action progressively affected, people may lose the ability to speak, eat, move and breathe. The motor nerves that are affected when you have ALS are the motor neurons that provide voluntary movements and muscle control. Examples of voluntary movements are making the effort to reach for a smart phone or step off a curb. These actions are controlled by the muscles in the arms and legs. Signs and symptoms might include:

·       Difficulty walking or doing normal daily activities

·       Tripping and falling

·       Weakness in your leg, feet or ankles

·       Hand weakness or clumsiness

·       Slurred speech or trouble swallowing

·       Muscle cramps and twitching in your arms, shoulders and tongue

·       Inappropriate crying, laughing or yawning

·       Cognitive and behavioral changes


Huntington’s disease (HD) is a fatal genetic disorder that causes the progressive breakdown of nerve cells in the brain. It deteriorates a person’s physical and mental abilities usually during their prime working years and has no cure. HD is known as the quintessential family disease because every child of a parent with HD has a 50/50 chance of inheriting the faulty gene. The symptoms of HD are described as having ALS, Parkinson’s and Alzheimer’s – simultaneously.

Symptoms usually appear between the ages of 30 to 50, and worsen over a 10 to 25-year period. Ultimately, the weakened individual succumbs to pneumonia, heart failure or other complications. Everyone has the gene that causes HD, but only those that inherit the expansion of the gene will develop HD and perhaps pass it on to each of their children. Every person who inherits the expanded HD gene will eventually develop the disease. Over time, HD affects the individual’s ability to reason, walk and speak.

·      Personality changes, mood swings & depression

·      Forgetfulness & impaired judgment

·      Unsteady gait & involuntary movements (chorea)

·      Slurred speech, difficulty in swallowing & significant weight loss


Huntington's disease is caused by an inherited defect in a single gene. Huntington's disease is an autosomal dominant disorder, which means that a person needs only one copy of the defective gene to develop the disorder.

With the exception of genes on the sex chromosomes, a person inherits two copies of every gene — one copy from each parent. A parent with a defective gene could pass along the defective copy of the gene or the healthy copy. Each child in the family, therefore, has a 50% chance of inheriting the gene that causes the genetic disorder.


Neuromuscular disease is a broad term that encompasses many diseases and ailments that impair the functioning of the muscles. These may directly involve the muscle directly or indirectly by involving the nerves or the Neuromuscular junction (the meeting point of the motor nerves and muscle fibre). The symptoms of Neuromuscular diseases may include- Numbness, painful abnormal sensation, muscle weakness, muscle atrophy, muscle pain or twitching (fasciculation). The Neuromuscular diseases may be categorised into the following groups:

·       Diseases of Anterior Horn Cells (Junction between spinal cord and motor nerve) – Motor Neurone Diseases

·       Diseases involving motor and sensory nerves – Peripheral Neuropathies

·       Disorders of the Neuromuscular function – Myasthenia Gravis and related diseases

·       Diseases of the muscles (Myopathies)- Muscular Dystrophy and Inflammatory myopathies


Blood Disorders

Thalassemia is a genetically inherited blood disorder which is characterized by the production of less or abnormal hemoglobin. As we know, hemoglobin is a protein found in Red Blood Cells. Hemoglobin is responsible for carrying oxygen around in the body. Thalassemia results in large numbers of red blood cells being destroyed, which leads to anemia. Anemia is a condition in which your body doesn’t have enough normal, healthy red blood cells. As a result of anemia, person affected with Thalassemia will have pale skin, fatigue and dark coloration of urine.

Thalassemia is inherited, meaning that at least one of your parents must be a carrier of the disorder. It’s caused by either a genetic mutation or a deletion of certain key gene fragments. Thalassemia minor is a less serious form of the disorder. There are two main forms of thalassemia that are more serious. In alpha thalassemia, at least one of the alpha globin genes has a mutation or abnormality. In beta thalassemia, the beta globin genes are affected.


Thalassemia beta

Beta thalassemia occurs when your body can’t produce beta globin. Two genes, one from each parent, are inherited to make beta globin. This type of thalassemia comes in two serious subtypes: thalassemia major (Cooley’s anemia) and thalassemia intermedia.

Thalassemia major

Thalassemia major is the most severe form of beta thalassemia. It develops when beta globin genes are missing.

The symptoms of thalassemia major generally appear before a child’s second birthday. The severe anemia related to this condition can be life-threatening. Other signs and symptoms include:

This form of thalassemia is usually so severe that it requires regular blood transfusions.

Thalassemia intermedia

Thalassemia intermedia is a less severe form. It develops because of alterations in both beta globin genes. People with thalassemia intermedia don’t need blood transfusions.

Thalassemia alpha

Alpha thalassemia occurs when the body can’t make alpha globin. In order to make alpha globin, you need to have four genes, two from each parent.

This type of thalassemia also has two serious types: hemoglobin H disease and hydrops fetalis.

Hemoglobin H

Hemoglobin H develops as when a person is missing three alpha globin genes or experiences changes in these genes. This disease can lead to bone issues. The cheeks, forehead, and jaw may all overgrow. Additionally, hemoglobin H disease can cause:

Hydrops fetalis

Hydrops fetalis is an extremely severe form of thalassemia that occurs before birth. Most babies with this condition are either stillborn or die shortly after being born. This condition develops when all four alpha globin genes are altered or missing.

Thalassemia and anemia

Thalassemia can quickly lead to anemia. This condition is marked by a lack of oxygen being transported to tissues and organs. Since red blood cells are responsible for delivering oxygen, a reduced number of these cells means you don’t have enough oxygen in the body either.

Your anemia may be mild to severe. Symptoms of anemia include:

Anemia can also cause you to pass out. Severe cases can lead to widespread organ damage, which can be fatal.


Thalassemia is caused by mutations in the DNA of cells that make hemoglobin — the substance in red blood cells that carries oxygen throughout your body. The mutations associated with thalassemia are passed from parents to children.

Hemoglobin molecules are made of chains called alpha and beta chains that can be affected by mutations. In thalassemia, the production of either the alpha or beta chains are reduced, resulting in either alpha-thalassemia or beta-thalassemia.

In alpha-thalassemia, the severity of thalassemia you have depends on the number of gene mutations you inherit from your parents. The more mutated genes, the more severe your thalassemia.

In beta-thalassemia, the severity of thalassemia you have depends on which part of the hemoglobin molecule is affected.


Four genes are involved in making the alpha hemoglobin chain. You get two from each of your parents. If you inherit:

·       One mutated gene, you'll have no signs or symptoms of thalassemia. But you are a carrier of the disease and can pass it on to your children.

·       Two mutated genes, your thalassemia signs and symptoms will be mild. This condition might be called alpha-thalassemia trait.

·       Three mutated genes, your signs and symptoms will be moderate to severe.

Inheriting four mutated genes is rare and usually results in stillbirth. Babies born with this condition often die shortly after birth or require lifelong transfusion therapy. In rare cases, a child born with this condition can be treated with transfusions and a stem cell transplant.


Two genes are involved in making the beta hemoglobin chain. You get one from each of your parents. If you inherit:

·       One mutated gene, you'll have mild signs and symptoms. This condition is called thalassemia minor or beta-thalassemia.

·       Two mutated genes, your signs and symptoms will be moderate to severe. This condition is called thalassemia major, or Cooley anemia.

Babies born with two defective beta hemoglobin genes usually are healthy at birth but develop signs and symptoms within the first two years of life. A milder form, called thalassemia intermedia, also can result from two mutated genes.


Factors that increase your risk of thalassemia include:

·       Family history of thalassemia. Thalassemia is passed from parents to children through mutated hemoglobin genes.

·       Certain ancestry. Thalassemia occurs most often in African Americans and in people of Mediterranean and Southeast Asian descent.

Hemophilia is a bleeding disorder that slows the blood clotting process. People with this condition experience prolonged bleeding or oozing following an injury, surgery, or having a tooth pulled. In severe cases of hemophilia, continuous bleeding occurs after minor trauma or even in the absence of injury (spontaneous bleeding). Serious complications can result from bleeding into the joints, muscles, brain, or other internal organs. Milder forms of hemophilia do not necessarily involve spontaneous bleeding, and the condition may not become apparent until abnormal bleeding occurs following surgery or a serious injury.


The two main types of hemophilia are A and B, according to the National Hemophilia Foundation. A third, rarer form of the disease is called hemophilia C. Each type is directly related to a specific factor, namely, hemophilia A is a Factor VIII deficiency, hemophilia B is a Factor IX deficiency and hemophilia C is a Factor XI deficiency.

Hemophilia type A

Hemophilia A is a genetic disorder caused by missing or defective Factor VIII protein. It is inherited, but in about one-third of known cases it is caused by a spontaneous genetic mutation.

The blood disorder affects all ethnic groups equally. More than half of all people with hemophilia A have a severe form of the disease.

Hemophilia A is carried by the X chromosome. It is inherited in an X-linked recessive manner. As such, two hemophilia-carrying X chromosomes must be inherited for the disease to be active in women, but only in one X chromosome for men.

A female inherits two XX chromosomes, one from her mother and one from her father (XX). A male inherits an X chromosome and a Y chromosome from her father (XY). This means that if a son inherits an X chromosome from his mother who carries hemophilia, he will have hemophilia. But because women receive two X chromosomes, only if both parents carry the defective gene can they develop the disease.

Hemophilia A has three stages: mild, moderate and severe, depending on the ratio of Factor VIII clotting protein in the blood. Mild hemophilia 6-49 percent, moderate hemophilia is 1-5 percent, and severe is less than 1 percent.

People with hemophilia A bleed longer than others, internally or externally. Those with mild hemophilia A generally bleed only after serious injury, trauma or surgery. Often, the disease is diagnosed after one of these situations due to prolonged bleeding, and the first episode may occur only in adulthood. Women often experience heavy menstrual periods and can hemorrhage after giving birth.

Moderate hemophilia patients tend to have more frequent bleeding episodes after less important injuries, or even spontaneously. In severe cases, bleeding may occur spontaneously in the joints and muscles.

Hemophilia A should be diagnosed and treated at a specialized hemophilia center. Tests that evaluate clotting time and a patient’s ability to form a clot may be ordered. A clotting factor test, called an assay, will determine the type of hemophilia and its severity.

The main treatment for hemophilia A is concentrated Factor VIII product, which is administered intravenously.

Patients with severe hemophilia may be given a routine treatment regimen called prophylaxis to maintain enough clotting factor in their bloodstream to prevent bleeds.

Hemophilia type B

Hemophilia B is a genetic disorder caused by missing or defective Factor IX clotting protein. It is also inherited, and just like hemophilia A, it can be caused by a spontaneous genetic mutation in one-third of the cases. This type of hemophilia also affects all ethnic groups equally, but it is about four times as rare as hemophilia A.

Hemophilia B is also carried in the X chromosome, in an X-linked recessive manner, meaning that two hemophilia-carrying X chromosomes must be inherited for the disease to be active in women, but only in one X chromosome in men.

Females inherit two XX chromosomes, one from their mother and one from their father (XX). Males inherit an X chromosome and a Y chromosome from their father (XY). This means that is a son inherits an X chromosome from his mother that has carries hemophilia, he will have hemophilia. But because women receive two X chromosomes, it’s only if the two carry the defective gene, that they develop the disease.

Severity levels are the same as hemophilia A, as well as symptoms.

Like hemophilia A, hemophilia B should be diagnosed at a specialized medical facility. Tests that evaluate clotting time and a patient’s ability to form a clot may be ordered. A clotting factor test, called an assay, will determine the type of hemophilia and its severity.

In hemophilia B, the most common treatment is the administration of concentrated Factor IX, administered intravenously. Severe cases of hemophilia B will also be on prophylaxis treatment, to maintain Factor IX clotting factor.

Hemophilia type C

Hemophilia C is a genetic disorder caused by missing or defective Factor XI clotting protein. The disease was first recognized in 1953 in patients who experienced severe bleeding after dental extractions.

The incidence of hemophilia C is estimated at one in every 100,000 people in the general population. In Israel, Factor XI deficiency occurs in up to 8 percent of Ashkenazi Jews due to intermarriage. This is because a Factor XI deficiency is inherited in an autosomal recessive pattern, meaning both parents must carry the gene to pass it on to their children. Unlike hemophilia A and B, men and women are affected equally.

Factor XI plays an important role in the clotting cascade, which leads to clotting. It helps generate more thrombin, a protein that converts fibrinogen to fibrin, which traps platelets and helps hold a clot in place.

Unlike hemophilia A and B, symptoms don’t correlate with Factor XI levels in the blood. People with lower levels may bleed less than those with higher levels of Factor XI. Patients often experience nosebleeds or soft tissue bleeds, as well as hemorrhaging after tooth extraction.

Many women may not know they’re deficient in Factor XI until they experience menorrhagia (heavy menstrual periods) or postpartum bleeding. In hemophilia C, joint and muscle bleeds are uncommon.

To diagnose hemophilia C, doctors will order a bleeding time test, platelet function tests, and prothrombin time (PT) and activated partial thromboplastin time (aPTT) tests.

Factor XI concentrates are unavailable in the United States as yet, so doctors normally treat hemophilia C with fresh frozen plasma. But because Factor XI is not concentrated in this treatment, large amounts may be necessary, which can lead to blood clots. This treatment must be administered carefully.

Fibrin glue is also used to maintain clots after mouth bleeds. When combined with fresh frozen plasma, it arrests bleeding after circumcision and hernia repair. Antifibrinolytics are used to control nose bleeds or bleeding after tooth extraction.


The major symptom is bleeding, either prolonged external bleeding or bruising after minor trauma or for no apparent reason. Symptoms vary depending on whether the patient has the mild, moderate, or severe form of the disorder:

People with hemophilia may have any type of internal bleeding, but most often it occurs in the muscles and joints, such as the elbows, knees, hips, shoulders and ankles. There may be no pain at first, but if the bleeding continues, the joint may become hot to the touch, swollen, and painful to move.

Repeated bleeding into the joints and muscles over time may cause permanent damage, such as joint deformity and reduced mobility.

Bleeding in the brain is a very serious problem for those with severe hemophilia. It may be life-threatening. Get medical help immediately if you have signs of bleeding, such as:


When you bleed, your body normally pools blood cells together to form a clot to stop the bleeding. The clotting process is encouraged by certain blood particles. Hemophilia occurs when you have a deficiency in one of these clotting factors.

There are several types of hemophilia, and most forms are inherited. However, about 30% of people with hemophilia have no family history of the disorder. In these people, an unexpected change occurs in one of the genes associated with hemophilia.

Acquired hemophilia is a rare variety of the condition that occurs when a person's immune system attacks clotting factors in the blood. It can be associated with:

·       Pregnancy

·       Autoimmune conditions

·       Cancer

·       Multiple sclerosis

Sickle Cell Disease is a group of blood disorders that causes red blood cells (RBCs) to become sickle-shaped, misshapen and break down. The oxygen-carrying capacity of such misshapen RBCs reduce significantly. Sickle cell anemia is an inherited red blood cell disorder in which there aren't enough healthy red blood cells to carry oxygen throughout your body. It is a genetically transferred disease. Red Blood Cells contain a protein called hemoglobin. This is the protein that binds oxygen and carry it to all the parts of the body.

A gene on chromosome 11 is responsible for producing hemoglobin protein. This gene sometimes becomes abnormal due to mutation. If a person inherits two abnormal copies of this gene, one from each parent, then that person will develop sickle cell disease. The sickle cell gene is passed from generation to generation in a pattern of inheritance called autosomal recessive inheritance. This means that both the mother and the father must pass on the defective form of the gene for a child to be affected. There's no cure for most people with sickle cell anemia. But treatments can relieve pain and help prevent complications associated with the disease.


Following are the most common types of SCD:


People who have this form of SCD inherit two sickle cell genes (“S”), one from each parent. This is commonly called sickle cell anemia and is usually the most severe form of the disease.


People who have this form of SCD inherit a sickle cell gene (“S”) from one parent and from the other parent a gene for an abnormal hemoglobin called “C”. Hemoglobin is a protein that allows red blood cells to carry oxygen to all parts of the body. This is usually a milder form of SCD.

HbS beta thalassemia

People who have this form of SCD inherit one sickle cell gene (“S”) from one parent and one gene for beta thalassemia, another type of anemia, from the other parent. There are two types of beta thalassemia: “0” and “+”. Those with HbS beta 0-thalassemia usually have a severe form of SCD. People with HbS beta +-thalassemia tend to have a milder form of SCD.

There also are a few rare types of SCD:

HbSD, HbSE, and HbSO

People who have these forms of SCD inherit one sickle cell gene (“S”) and one gene from an abnormal type of hemoglobin (“D”, “E”, or “O”). Hemoglobin is a protein that allows red blood cells to carry oxygen to all parts of the body. The severity of these rarer types of SCD varies.



People who have SCT inherit one sickle cell gene (“S”) from one parent and one normal gene (“A”) from the other parent. This is called sickle cell trait (SCT). People with SCT usually do not have any of the signs of the disease and live a normal life, but they can pass the trait on to their children. Additionally, there are a few, uncommon health problems that may potentially be related to sickle cell trait.


Signs and symptoms of sickle cell anemia usually appear around 5 months of age. They vary from person to person and change over time. Signs and symptoms can include:

·       Anemia. Sickle cells break apart easily and die, leaving you with too few red blood cells. Red blood cells usually live for about 120 days before they need to be replaced. But sickle cells usually die in 10 to 20 days, leaving a shortage of red blood cells (anemia).

Without enough red blood cells, your body can't get enough oxygen, causing fatigue.

·       Episodes of pain. Periodic episodes of pain, called pain crises, are a major symptom of sickle cell anemia. Pain develops when sickle-shaped red blood cells block blood flow through tiny blood vessels to your chest, abdomen and joints. Pain can also occur in your bones.

The pain varies in intensity and can last for a few hours to a few weeks. Some people have only a few pain crises a year. Others have a dozen or more pain crises a year. A severe pain crisis requires a hospital stay.

Some adolescents and adults with sickle cell anemia also have chronic pain, which can result from bone and joint damage, ulcers, and other causes.

·       Swelling of hands and feet. The swelling is caused by sickle-shaped red blood cells blocking blood flow to the hands and feet.

·       Frequent infections. Sickle cells can damage your spleen, leaving you more vulnerable to infections. Doctors commonly give infants and children with sickle cell anemia vaccinations and antibiotics to prevent potentially life-threatening infections, such as pneumonia.

·       Delayed growth or puberty. Red blood cells provide your body with the oxygen and nutrients needed for growth. A shortage of healthy red blood cells can slow growth in infants and children and delay puberty in teenagers.

·       Vision problems. Tiny blood vessels that supply your eyes can become plugged with sickle cells. This can damage the retina — the portion of the eye that processes visual images — and lead to vision problems.


Mutations in the HBB gene cause sickle cell disease.

Hemoglobin consists of four protein subunits, typically, two subunits called alpha-globin and two subunits called beta-globin. The HBB gene provides instructions for making beta-globin. Various versions of beta-globin result from different mutations in the HBB gene. One particular HBB gene mutation produces an abnormal version of beta-globin known as hemoglobin S (HbS). Other mutations in the HBB gene lead to additional abnormal versions of beta-globin such as hemoglobin C (HbC) and hemoglobin E (HbE). HBB gene mutations can also result in an unusually low level of beta-globin; this abnormality is called beta thalassemia.

In people with sickle cell disease, at least one of the beta-globin subunits in hemoglobin is replaced with hemoglobin S. In sickle cell anemia, which is a common form of sickle cell disease, hemoglobin S replaces both beta-globin subunits in hemoglobin. In other types of sickle cell disease, just one beta-globin subunit in hemoglobin is replaced with hemoglobin S. The other beta-globin subunit is replaced with a different abnormal variant, such as hemoglobin C. For example, people with sickle-hemoglobin C (HbSC) disease have hemoglobin molecules with hemoglobin S and hemoglobin C instead of beta-globin. If mutations that produce hemoglobin S and beta thalassemia occur together, individuals have hemoglobin S-beta thalassemia (HbSBetaThal) disease.

Abnormal versions of beta-globin can distort red blood cells into a sickle shape. The sickle-shaped red blood cells die prematurely, which can lead to anemia. Sometimes the inflexible, sickle-shaped cells get stuck in small blood vessels and can cause serious medical complications.