Food shortages and an epidemic of optic and peripheral neuropathy in Cuba.

From late 1991 to mid-1993, cases of optic neuropathy of unknown etiology, which first appeared in unusual numbers in a western province of Cuba, spread and multiplied throughout the island. The dominant symptoms changed, becoming increasingly those of peripheral neuropathy. Incidence rates peaked in April 1993. An estimated 50,000 cases were reported. The majority were adult men and women (aged about 25-65), with comparatively few children or elderly people being affected. The cause has yet to be delineated. However, food shortages and radical changes in diet resulting from the longstanding US trade embargo and the recent loss of Eastern Europe as Cuba's trading partner have compromised nutritional status, especially B-vitamin sufficiency, and appear to be related to the neuropathic illnesses. In April 1993, the Cuban government began distributing vitamin supplements to every citizen. Causal hypotheses include tobacco-alcohol or "nutritional" amblyopia; cyanide toxicity from cassava; toxic legumes introduced as supplements to scarce flour; other toxins, for example pesticides, or a "blue mold" on tobacco; enterovirus; and a hereditary enzyme deficiency in affected persons. None of these factors appears to be present in all cases, but it is generally believed that an interaction of some toxin or toxins, in combination with nutritional deficiency, is likely to be the major cause.