Heavy Metal Poisoning

Introduction to Heavy Metal Poisoning - Toxic Titans Overview

• Definition: Dense metals/metalloids toxic at low exposures.
• Sources: Environmental (water, soil), occupational, accidental, pica, traditional medicines.
• Mechanisms: Enzyme inhibition, oxidative stress, binding sulfhydryl (-SH) groups.
• Clues: Multi-systemic effects; symptoms disproportionate to common illnesses.
• Diagnosis: History (exposure, occupation), exam, basic labs, specific metal screening.

⭐ Many heavy metals exert toxicity by binding sulfhydryl (-SH) groups in proteins, disrupting function.

Lead Poisoning - Plumbism's Punch

• Sources: Old paint, batteries, pipes, traditional cosmetics (Surma).
• Clinical Features:
  • Children: Neurodevelopmental delay, encephalopathy, behavioral changes.
  • Adults: Peripheral neuropathy (wrist/foot drop), abdominal colic, constipation, microcytic anemia (basophilic stippling), Burtonian line, renal dysfunction.
• Diagnosis: Blood Lead Level (BLL), X-ray (lead lines in long bones of children; radiopaque paint chips in GIT), ↑Erythrocyte protoporphyrin (EP).
• Management: Remove exposure. Chelation based on BLL (action level >5 µg/dL):
  • Children: Succimer (DMSA) if BLL ≥45 µg/dL.
  • Severe (BLL >70 µg/dL)/Encephalopathy: CaNa2EDTA + Dimercaprol (BAL).
• 📌 Mnemonic 'LEAD': Lead lines, Encephalopathy/Erythrocyte stippling, Abdominal colic/Anemia, Drop foot/wrist.

⭐ Basophilic stippling of red blood cells is a classic finding in lead poisoning, though not entirely specific.

Arsenic Poisoning - Arsenic's Assault

• Sources: Groundwater, pesticides, industry, traditional meds. Forms: Inorganic (↑toxic)/Organic.
• Acute: GIT (rice-water stool), garlic odor, hypotension, QTc ↑, encephalopathy.
• Chronic: Skin (raindrop pigment, hyperkeratosis, Mees' lines), neuropathy, anemia, cancers.
• Dx: Urine (acute), hair/nail (chronic).
• Rx: Supportive, decontamination, Chelation (BAL; DMSA/DMPS).
• 📌 ARSENIC: Anemia, Raindrop skin, Sensory neuropathy, Encephalopathy, Nail (Mees'), Intestinal colic, Cancers.

⭐ Chronic arsenic exposure is infamously linked to characteristic skin changes like raindrop pigmentation and palmar/plantar hyperkeratosis, as well as an increased risk of various cancers.

Mercury Poisoning - Quicksilver Crisis

• Forms & Sources:
  • Elemental (vapor): Thermometers, dental amalgams.
  • Inorganic salts (ingestion): Batteries, disinfectants.
  • Organic (methylmercury, ingestion): Contaminated fish.
• Clinical Features:
  • Elemental: Pneumonitis, tremor, erethism ('Mad Hatter').
  • Inorganic: Corrosive gastroenteritis, renal failure (ATN).
  • Organic: Neurotoxic (Minamata disease - paresthesias, ataxia); teratogenic.
  • Acrodynia ('pink disease') in children.
• Diagnosis: Blood/urine mercury.
• Management: Remove exposure. Chelation: DMSA, DMPS. ⚠️ BAL contraindicated for methylmercury. 📌 MERCURY: Mad hatter, Erethism, Renal, CNS, Ulcerative gingivostomatitis, Respiratory, Yummy fish.

⭐ Methylmercury bioaccumulates in fish, causing Minamata disease (severe neurological damage).

Iron & Chelation Therapy - Ferrous Fright & Metal Mop-Up

• Iron Poisoning (Acute, Children):
  • Stages: GIT (0-6h) → Latent (6-24h) → Systemic (12-48h: shock, acidosis) → Hepatic failure → Strictures.
  • Dx: Serum Fe (peak 4-6h), AXR (radiopaque).
  • Rx: Supportive, WBI. IV Deferoxamine if severe (Fe > 500 µg/dL, shock, acidosis).

    ⭐ Deferoxamine, the chelator for iron poisoning, characteristically turns the urine a 'vin rosé' (pinkish-orange) color when iron is being excreted.

• Chelation: Forms stable, excretable complexes.
  • Key Chelators:
    • Deferoxamine (Fe): IV/IM.
    • BAL (Dimercaprol) (As, Pb, Hg): IM, painful.
    • CaNa2EDTA (Pb): IV/IM, nephrotoxic.
    • DMSA (Succimer) (Pb, As, Hg): Oral.

High‑Yield Points - ⚡ Biggest Takeaways

• Lead poisoning: Basophilic stippling, Burton's line, neuropathy (wrist/foot drop). Antidotes: EDTA, DMSA, BAL.
• Arsenic poisoning: Garlic breath, Mees' lines, skin changes. Antidotes: BAL, DMSA.
• Mercury poisoning: Tremors, erethism, acrodynia (children). Antidotes: BAL, DMSA, DMPS.
• Iron toxicity: Managed with deferoxamine (causes vin rosé urine).
• Copper (Wilson's disease): Kayser-Fleischer rings. Chelator: Penicillamine.
• Thallium poisoning: Alopecia, painful neuropathy. Antidote: Prussian blue.
• Dimercaprol (BAL): Contraindicated in iron and cadmium poisoning.