Chronic mercury poisoning developed in two patients following long-term daily ingestion of a laxative preparation containing mercurous chloride (calomel). There were major clinical manifestations attributable to toxic effects of mercury on the kidneys, gastrointestinal tract and central nervous system. Chronic renal failure developed in both patients and was manifested by elevated serum urea nitrogen and creatinine levels, with proteinuria but no abnormalities in the urinary sediment. Both patients showed evidence of renal tubular defects. Both patients had colitis with intractable watery diarrhea. In one, the colitis was so severe as to require a diverting colostomy. Dementia was present in both patients, with tremor a prominent feature in one. Tissue mercury levels were highest in the colon (526 μg/g; normal 0.10 μg/g) and kidney (421 μg/g; normal 2.75 μg/g); levels were also significantly elevated in the liver, brain, heart, pancreas, hair, skin, blood and urine. At autopsy both patients showed melanosis coli and blackening of the renal cortex. By electron microscopy the pseudomelanin granules in the colon were atypical in that they were intimately associated with ultra dense crystals identified by electron diffraction as beta mercuric sulfide. Crystals of beta ercuric sulfide were also associated with lipofuscin deposits in renal tubular epithelium and were present free and within macro-phages of the renal cortical interstitium and hepatic portal triads. Chronic mercury poisoning due to mercurous chloride-containing laxative preparations should be suspected in patients with a history of laxative abuse who present with unexplained renal failure, colitis, dementia or tremor.
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