Chronic Manganese Intoxication

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Abstract
Six men developed chronic manganese intoxication while employed in a manganese ore crushing plant. Symptoms included somnolence, gait imbalance, slurred speech, and impaired fine movements. Signs included bradykinesia, postural instability, impaired arising ability, masked facies, and speech disorder. One patient was exceptional in that his major symptoms did not develop until three years after leaving exposure. Levodopa, up to 8 gm/day, was ineffective in three patients. Our cases and those in the literature indicate that, in the absence of rigidity or dystonia or both, levodopa is ineffective in chronic manganese intoxication. Intravenous edetic acid (EDTA) infusions were followed by temporary improvement in four individuals. Increased urinary excretion of manganese during edetic acid infusion was observed in our cases and in two controls and thus does not appear to assist in diagnosing chronic manganese intoxication.