Forensic onychology of heavy metal exposure: forensic dermatology of the manifestations of heavy metal toxicity in nails.

Fingernails and toenails can be an important source of trace evidence at a crime scene investigation. Arsenic, gold, lead, mercury, selenium, silver, and thallium are heavy metals; exposure to these metals can result not only in dyschromia of the nail, but also dystrophy of the nail plate. Mees lines, either single or multiple transverse white bands on the nail, were originally described in association with arsenic exposure. Similar white horizontal bands of transverse leukonychia have also been observed in patients following exposure to selenium and thallium. A diagnostic clue for persons who investigate forensic crime scenes to the possibility of heavy metal toxicity in the victim can be changes in the fingernails and toenails. The nails can be photographed and subsequently analyzed for the presence of the causative metal when the possibility of heavy metal exposure is entertained by crime scene investigators and/or medical examiners or coroners.