Three food-related neurotoxic disorders, lathyrism, konzo, and tropical ataxic neuropathy, are special challenges to mankind because factors producing these disorders are linked to lack of education, poverty, population growth, and certain conditions like drought, trade, and war. Lathyrism is a form of irreversible, nonprogressive spastic paraparesis associated with poorly understood degenerative changes in the spinal cord, and it is caused by long-term and excessive consumption of the grass pea Lathyrus sativus. The pathological demyelinating changes in neurolathyrism largely involve pyramidal tracts. The longest pyramidal neurons are more severely affected. The disease is presently restricted to India, Bangladesh, and Ethiopia. In areas of India where a high consumption of Lathyrus sativus was previously reported, increased awareness has led to marked reduction in lathyrism cases. Nutritional deficiencies of sulfur amino acid methionine and cysteine aggravate the neurotoxicity of beta-N-oxalyl amino-L-alanine. Cassava leaves (Manihot esculenta Crantz) constitute the main daily source of protein as supplement to the major staple food in remote rural areas of Africa. Ingestion of large amounts of poorly processed cassava roots is associated with the occurrence of an epidemic form of a noncompressive myelopathy (konzo) in African countries. Konzo is a neurologic entity with selective upper motor neuron damage and is characterized by an abrupt onset of an irreversible, nonprogressive, and symmetrical spastic paraparesis or tetraparesis. A ‘‘wetting method’’ has been reported to eradicate or markedly reduce konzo outbreaks in the Democratic Republic of Congo. A study on rats noted that Ginkgo biloba extracts can prevent motor changes associated with cassava juice consumption (41). The occurrence of another toxic disease in Africa, tropical ataxic neuropathy, is attributed to prolonged dietary cyanide exposure. Minor improvements in food processing have been found effective in the prevention of these disabling neurotoxic disorders. In this article, the author provides updated information on epidemiology, clinical features, differential diagnosis, and management of lathyrism, konzo, and tropical ataxic neuropathy. The author also discusses a review that presents a unifying hypothesis on the causative agents for lathyrism, konzo, and tropical ataxic neuropathy.
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• Three food-related neurotoxic disorders, lathyrism, konzo, and tropical ataxic neuropathy, are linked to illiteracy, poverty, population growth, and conditions like drought, famine, and war.
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• Lathyrism is an irreversible, nonprogressive spastic paraparesis resulting from excessive consumption of peas of Lathyrus sativus.
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• Lathyrus sativus contain a neurotoxin, beta-N-oxalyl amino-L-alanine (synonym beta-N-oxalyl-L-alpha,beta-diaminopropionic acid).
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• Konzo is also a distinct form of tropical myelopathy that appears abruptly because of excessive consumption of roots of bitter cassava.
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• Tropical ataxic neuropathy is a neurologic syndrome of sensory polyneuropathy, gait ataxia, optic atrophy, and sensory deafness resulting from the dietary use of large quantities of cassava for long periods of time.
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• There is no specific treatment for any of these entities. A good diet containing high doses of vitamins and physical rehabilitation are required.
Historical note and terminology
Lathyrism results from excessive consumption of the chickling pea, Lathyrus sativus, and certain related species. It is one of the oldest neurotoxic diseases known to mankind. Devastating neurolathyrism epidemics have occurred during major famine crises in various parts of the world. Hippocrates (c.460 to c.377 BC) is believed to have been aware of the toxic pea causing persistent paralysis of the legs. In 1873, the Italian scientist Contani coined the term “lathyrismo” (lathyrism) in patients with progressive spastic paraparesis (05). In 1947, Kessler published a vivid account of the toxicity of L sativus among the Romanian prisoners of war during the Second World War (20). The toxic constituent of L sativus is an amino acid identified as beta-N-oxalyl amino-L-alanine. In 1964, 2 groups of Indian scientists identified beta-N-oxalyl amino-L-alanine after primate feeding studies (29; 42).
Konzo was first described by Trolli in 1936 in Zaire (48). In the Yaka language, konzo means “tied legs,” a description of the spastic gait. This is the name used in Congo, and it is now the official term for this pure motor neuron disorder. Lancaster and colleagues were the first to report that prolonged consumption of cassava caused konzo (23).
The term “tropical ataxic neuropathy” was first used by Osuntokun in Nigeria in 1968 (38). Osuntokun established that this condition developed due to chronic dietary cyanide exposure. A similar form of endemic neuropathy in the Caribbean, which was popularly known as “Jamaican Neuropathy,” was described at least a century ago. Although it was thought that this condition had ceased to occur about 2 decades ago, a study has shown that this disease is still endemic in certain areas of the world (35).