[Intention and action myoclonus disclosing occupational mercury poisoning]

A 58-year-old laboratory-glassware manufacturer was referred to hospital because of coarse "tremor" of the upper extremities of 16-months-duration. Examination showed severe intention and action myoclonus, confirmed by electromyographic recording, slight memory impairment but was otherwise normal. Mercury levels were high in blood and urine (not in CSF) and, as other causes of myoclonus were excluded, inorganic mercury poisoning, was diagnosed. Only slight unilateral intention tremor persisted after dimercaprol treatment. Inhalation of mercury vapor was the mode of contamination. Myoclonus is the hallmark of severe inorganic mercury intoxication, the main clinical and pathological aspects of which are briefly discussed.