FM13.13 | Metallic Poisons (Arsenic, Lead, Mercury, Copper, Iron) — Summary & Reflection

KEY TAKEAWAYS

Metallic poisons (FM13.13) comprise five agents with distinct clinical signatures and chelation strategies:

• Arsenic: garlic odour; Mees' lines (transverse white nail bands — each = one exposure episode); rain-drop pigmentation; Marsh test/Reinsch test/AAS. Chelator: BAL (dimercaprol) or DMSA.

• Lead: Burton's line (gingival); basophilic stippling; wrist drop/foot drop; lead lines on X-ray. Chelator: Ca-EDTA (IV, severe) or DMSA (oral, moderate).

• Mercury: erethism + tremor (elemental); gingivostomatitis; Hunter-Russell syndrome (organic). Chelator: BAL or DMSA.

• Copper (CuSO₄): blue-green vomitus; haemolysis → haemoglobinuria. Chelator: D-penicillamine.

• Iron: four-phase course; haemorrhagic GI → latent → metabolic acidosis + hepatic failure → GI strictures. Chelator: deferoxamine ONLY (BAL contraindicated). Vin rosé urine confirms active chelation.

Medicolegal significance: arsenic most important for homicidal poisoning; lead/mercury primarily occupational; copper suicidal/homicidal in India; iron paediatric accidental.

REFLECT

You are advising a magistrate on a suspected chronic arsenic poisoning case — the alleged victim is alive but unwell, and the alleged perpetrator (a household member) denies involvement. The victim's fingernails show Mees' lines at 6 mm and 12 mm from the nail fold. Using what you know about nail growth rate and Mees' lines: what does this evidence suggest about the timing and pattern of exposure? What additional specimens would maximise the evidentiary value of your analytical findings? And how would you explain the significance of Mees' lines to a non-medical judge in simple, verifiable terms?