The clinical, neuropsychological, and radiological features of a family, and the toxicological and neuropathological findings of one family member, who were acutely and severely intoxicated with methylmercury are reported after a 22-year follow-up from the Albuquerque Veterans Affairs Medical Center, the University of New Mexico School of Medicine, and the Environmental Health Sciences Center, the University of Rochester School of Medicine, NY. In 1969 a family in New Mexico had consumed pork containing methylmercury. Three children and a neonate developed severe neurological signs. At 22-year follow-up, the 2 oldest patients, ages 42 and 35 years, had cortical blindness, impaired stereognosis and graphesthesia, poor hand coordination, ataxia, choreoathetosis, dysarthria, and attentional deficits. MRIs showed loss of tissue in calcarine cortices, parietal lobes, and cerebellar folia. The 2 youngest were quadriplegic, blind, and mentally retarded and they died at ages 29 and 21 years. The brain of the patient poisoned at 8 years and dying at 29 showed cortical atrophy, neuronal loss and gliosis. Total mercury level in the occipital cortex was 1,974 ng/gm, 50 times that of a control; the Hg was mainly inorganic. Hair and systemic organs had Hg levels comparable to controls. [1]

COMMENT. Methylmercury crosses the blood-brain barrier easily while inorganic mercury does not. Biotransformation to inorganic Hg over time may account for the high level of inorganic Hg and absence of methyl Hg in the patient’s brain at autopsy. The possible role of inorganic Hg in the brain damage is debatable; it is usually considered to be inert and nontoxic. See Environmental Poisons in Food, Chicago, PNB Publishers, 1993, for an account of the sources, metabolism, epidemiology, clinical manifestations, treatment, and prevention of mercury poisoning. Accidental exposure to mercury vapor is a persisting hazard in nurseries with broken thermometers and in school science labs. The symptoms of mild exposure, micromercurialism, are subtle and difficult to diagnose without a high index of suspicion. Acrodynia, or Pink disease, is a relatively rare occurrence, but a diagnosis which should be familiar to the pediatric neurologist and pediatrician.