PH9.3 | PH9.3 | Heavy Metal Poisoning and Chelation — SDL Guide — Summary & Reflection

KEY TAKEAWAYS

Heavy metals cause toxicity primarily through SH-group binding (lead, mercury, arsenic) or free radical generation (iron) or enzyme-specific disruption (copper). Key clinical fingerprints: Lead — basophilic stippling, lead lines (gingival/metaphyseal), wrist/foot drop (adults), encephalopathy (children); Mercury — inorganic→Fanconi-like renal syndrome, organic→Minamata cerebellar/sensory disease; Arsenic — Mees' lines, keratosis, 'rice water' diarrhoea, carcinogen; Iron — 5 stages (GI → quiescent → systemic → hepatic → GI stricture); Copper (Wilson's) — liver + neuropsychiatric + Kayser-Fleischer rings. Chelator-metal pairs: Lead encephalopathy → BAL IM first then EDTA IV (4-hour rule); lead non-encephalopathic → DMSA oral; Iron → Deferoxamine (vin rosé urine; BAL CONTRAINDICATED for iron); Wilson's copper → D-penicillamine (lifelong; trientine second-line); Arsenic/mercury → DMSA or DMPS. BAL absolute contraindications: iron, cadmium. EDTA: for lead only (not mercury, not arsenic). D-penicillamine ADRs: aplastic anaemia, nephropathy, lupus, myasthenia — monthly monitoring required. Never stop Wilson's disease chelation abruptly.

REFLECT

Consider the Minamata disease tragedy in Japan in the 1950s: a chemical plant discharged methylmercury-contaminated wastewater into Minamata Bay; local communities who relied on fish from the bay developed devastating neurological disease. Infants born to exposed mothers developed severe congenital disease. The disease was only recognised after years of investigation. Reflect on: What does this history tell us about the relationship between industrial activity and environmental health? How would a physician today identify an outbreak of heavy metal toxicity in a community (what would the first clues be)? What is the role of pharmacology versus public health policy in preventing heavy metal disease? Can chelation therapy restore function in Minamata disease patients? Why or why not?