Intoxication due to alkylmercury-treated seed--1971-72 outbreak in Iraq: clinical aspects.

Sixty-six hospitalized patients suffering from chronic methylmercury poisoning were examined in Baghdad during 1972. The poisoning was attributed to consumption of home-made bread prepared from seed wheat treated with mercurial fungicide. The age incidence ranged between 4 and 70 years.Of the various clinical features encountered, neurological symptoms and signs were predominant and included muscular weakness, numbness, unsteady gait, paraesthesia, dysarthria, mental disturbances and, in severe cases, blindness, partial deafness, stupor, coma, and death. Involvement of the cardiovascular, urinary, gastrointestinal and haemopoietic systems, which was commonly encountered in ethylmercury poisoning in the 1960 outbreak in Iraq, was unusual.The severity of symptoms and signs was, broadly speaking, dose-dependent; high exposure led to severe clinical manifestations, but variations existed. Criteria, based on the clinical manifestations, were set for grading the severity of cases. The series included 2 asymptomatic cases, 20 mild, 20 moderate, 14 severe, and 10 very severe. In the latter group 5 patients died from failure of the central nervous system.The severely poisoned patients died irrespective of the medical treatment received. After 2 years of observation, most patients graded as mild or moderate cases lost their symptoms completely. Severe cases improved slowly, although ataxia, diminution of visual field and acuity and paraesthesia were still present. Thus, the previously accepted view that neurological signs were irreversible has been disproved.