LATHYRISM

Lathyrism, one of the oldest neurotoxic diseases known to Man, results from excessive consumption of the chickling pea, Lathyrus sativus, and certain related species.

Lathyrism is a disease caused by eating seeds of species of Lathyrus (the grass pea), mainly L. sativus (the chickling pea or khesari), L. cicera (flat-podded vetch) and L. clymenum (Spanish vetchling). It affects mostly people in Bangladesh, India, Pakistan, Nepal and Algeria but is sometimes found in France, Italy, Spain and Australia. This disease affects horses and cattle as well as in man. Beta-oxalyl-amino-L-alanine acid (BOAA), an excitatory neurotoxin and glutamate agonist, has been identified as the constituent of the chickling pea responsible for the disease. BOAA appears to exert its effects through mitochondrial toxicity.

The first record of the disease is thought to be an ancient Hindu work called Bhavaprakasa but it was also described by Hippocrates around 400 BC. A survey in India in 1833 reported the disease in poor people during a drought but it was not until 1873 that Cantani in Italy named the disease as lathyrism.

Lathyrism is a form of irreversible, non-progressive spastic paraparesis associated with poorly understood degenerative changes in spinal cord. Domestic animals, notably the horse, also develop hindlimb paralysis after prolonged feeding on lathyrus fodder.

Symptoms

· The onset of neurolathyrism is usually sudden and coincident with the monsoon season. Early symptoms include:

o Walking difficulties

o Unbearable cramps

o Leg weakness

· Spastic paralysis develops which becomes irreversible.

· Pyramidal tract involvement causes:

o Motor weakness

o Increased tone

o A lurching scissoring gait caused by involvement of the thigh extensors and adductors and gastrocnemius

o Extensor plantar responses

o Very brisk knee and ankle tendon reflexes, often clonic

o Hoffmann's sign and exaggerated biceps and/or triceps tendon jerks in the most severely affected

· There are no objective sensory signs but perverse sensations in the legs are frequently reported at the onset. Walking difficulties often begin suddenly but may also appear subacutely or insidiously. Some people experience partly reversible symptoms suggestive of a diffuse CNS excitation of somatic, motor and autonomic function.Spasticity can be more marked than the motor weakness.

· Lathyrism is not simply a paralytic syndrome, as angiolathyrism causes sudden death: the toxin changes the elasticity of the aorta causing aortic aneurysm that may rupture.

· Osteolathyrism affects skeletal development: cartilages and bones grow abnormally leaving the body deformed. Children suffer skeletal deformity and poor cerebral development.

Causes

· Cooking with clay implements

· Eating green unripe and boiled pea forms

· Blood group O