A man presents with severe epistaxis, gingival bleeding, alopecia, Mees' lines on his fingernails, and painful peripheral neuropathy over 3 months. Hair analysis by atomic absorption spectrophotometry shows elevated levels of a heavy metal. Which metal is most likely, and through which mechanism does it produce Mees' lines?
- A Arsenic — deposited in keratinous tissues during the telogen phase, disrupting keratin cross-linking to form transverse white bands ✓
- B Lead — interferes with haem synthesis causing iron-deficiency-like anaemia
- C Mercury — binds thiol groups in peripheral nerves causing demyelination
- D Thallium — induces alopecia and neurological toxicity via potassium channel disruption
Explanation
Mees' lines (true leukonychia striata, transverse white bands on nails) are pathognomonic for chronic arsenic poisoning. Arsenic is incorporated into growing keratin (nails, hair) during periods of acute toxicity; the deposited arsenic disrupts disulfide bonds in keratin and appears as white transverse bands. Hair analysis by AAS showing elevated arsenic confirms chronic exposure. The other features — Aldrich-Mees lines in nails, Beau's lines (transverse nail ridges), Malpighian keratosis, rain-drop pigmentation of skin, and peripheral neuropathy — comprise the classic arsenic toxidrome.
Reference: The Essentials of Forensic Medicine and Toxicology (Narayan Reddy), 34th ed.
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Written and medically reviewed by the StethoPrep medical team.