## Characteristic Cutaneous Findings in Chronic Arsenic Poisoning **Key Point:** Mees' lines (also called Aldrich-Mees lines) are horizontal white lines on the nails that appear 2–3 months after arsenic exposure and are pathognomonic for chronic arsenic poisoning. ### Clinical Features of Chronic Arsenic Poisoning | Feature | Timing | Mechanism | |---------|--------|----------| | **Mees' lines** | 2–3 months post-exposure | Arsenic binds to keratin in nail matrix; appears as horizontal white bands | | **Hyperkeratosis** | Weeks to months | Thickening of palms and soles | | **Hyperpigmentation** | Chronic exposure | Melanin deposition in skin | | **Peripheral neuropathy** | Months | Axonal degeneration | | **Bowen's disease** | Years | Squamous cell carcinoma in situ | **High-Yield:** Mees' lines are: - Transverse white bands crossing the entire nail width - Appear in multiple nails simultaneously - Move distally as the nail grows (can be used to estimate timing of exposure) - May also occur with other heavy metals (thallium) and severe illness, but arsenic is the classic association **Clinical Pearl:** The presence of Mees' lines in a patient with a history of occupational or intentional exposure is strong forensic evidence of arsenic poisoning and can help establish a timeline of exposure. **Mnemonic:** **MEES** = **M**ultiple nails, **E**ven distribution, **E**xposure marker, **S**imultaneous appearance.
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