Heavy Metal Poisoning

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Intro to Heavy Metals - Toxic Titans Intro

  • Dense metals (e.g., Pb, Hg, As, Cd) toxic at low levels.
  • Sources: Widespread environmental (water, soil, air) and occupational exposures.
  • Characteristics: Bioaccumulate in tissues, persist in the body, non-degradable.
  • Primary toxicity: Disrupt vital enzyme functions and cellular structures.

    ⭐ Most heavy metals exert toxicity by binding to sulfhydryl (-SH) groups of enzymes, impairing their activity. Glutathione and its role in detoxification an

Lead Poisoning - Plumbism Perils

  • Sources: Old paint, batteries, pipes, some traditional medicines, occupational exposure.
  • Pathophysiology: Inhibits heme synthesis enzymes (ALA dehydratase, ferrochelatase) → ↑ALA, ↑protoporphyrin.
  • Clinical Features: 📌 LEAD
    • Lines: Burtonian (blue-black, gingival), lead lines (X-ray long bones).
    • Encephalopathy (esp. children), Erythrocyte basophilic stippling.
    • Anemia (microcytic, hypochromic), Abdominal colic.
    • Drop (wrist/foot due to peripheral neuropathy).
  • Diagnosis:
    • Blood Lead Level (BLL): Concern >3.5 µg/dL; Chelation (children) >45 µg/dL.
    • ↑Urinary ALA, ↑Free Erythrocyte Protoporphyrin (FEP).
  • Management: Remove source, Chelation therapy (e.g., Succimer/DMSA, CaNa2EDTA).

⭐ Basophilic stippling of RBCs is a characteristic (though not pathognomonic) finding in lead poisoning.

Chronic Lead Poisoning: Symptoms, Diagnosis, and Treatment

Mercury Poisoning - Quicksilver Quandaries

  • Forms: Elemental (Hg⁰), Inorganic (Hg⁺/Hg²⁺ salts), Organic (Methyl-, Ethyl-mercury).
  • Elemental (Inhaled vapor):
    • 📌 'Mad Hatter': Tremors, Erethism (irritability, excitability), Gingivostomatitis.
    • Acute: Pneumonitis.
  • Inorganic (Ingested salts):
    • GI: Corrosive gastroenteritis, bloody diarrhea.
    • Renal: Acute Tubular Necrosis (ATN).
  • Organic (Methylmercury - Ingested, e.g., fish):
    • Neurotoxic: Paresthesias, ataxia, dysarthria, visual/hearing loss.
    • Teratogenic.

    ⭐ Minamata disease, characterized by severe neurological damage, is caused by methylmercury poisoning, classically from contaminated fish.

  • Acrodynia (Pink Disease): Children; painful, pink extremities, hypertension, rash.
  • Diagnosis: Blood/urine mercury levels; forensic imaging (X-ray, CT, MRI) for detecting mercury deposits in chronic cases or post-mortem analysis.
  • Treatment: Chelation (Dimercaprol, DMSA, DMPS).

💡 Forensic Pearl: Advanced imaging techniques including CT and MRI can reveal mercury accumulation patterns in brain tissue, particularly valuable in chronic poisoning cases under BNS provisions for poisoning offenses.

Mercury Cycle and Bioaccumulation in Aquatic Ecosystems

Arsenic Poisoning - Arsenic's Agony

  • Sources: Global health issue from contaminated groundwater, pesticides, industrial exposure, intentional acts (suicide/homicide under BNS provisions).

  • Mechanism: Binds sulfhydryl groups, inhibits pyruvate dehydrogenase.

  • Acute:

    • Severe gastroenteritis (rice-water stools), garlic odor (breath/feces).
    • Hypotension, shock, encephalopathy.
  • Chronic:

    • Skin: Raindrop pigmentation, palmar/plantar hyperkeratosis, Bowen's disease.
    • Nails: Mees' lines.
    • Peripheral neuropathy (stocking-glove).
    • Cancers: Skin (SCC), lung, bladder.
  • Diagnosis: Blood arsenic (acute), 24hr urine arsenic, hair/nail analysis (chronic), clinical presentation, patient history.

  • Treatment: Supportive; Chelators (Dimercaprol/BAL, DMSA). Fatal dose: Variable based on arsenic form, individual susceptibility, exposure route.

⭐ Mees' lines (transverse white bands on nails) are a classic sign of chronic arsenic poisoning.

Management & Chelators - Metal Detox Tactics

  • Priorities: Supportive (ABCDEs), stop absorption, hasten elimination, chelators.
  • Chelation: Binds metals for excretion. Choice metal/patient-specific.

⭐ Dimercaprol (BAL) is contraindicated in iron, cadmium, and selenium poisoning as it can form more toxic complexes and redistribute arsenic to the brain if given alone in acute arsenic CNS toxicity.

High‑Yield Points - ⚡ Biggest Takeaways

  • Lead: Burton's line, basophilic stippling, wrist/foot drop, colic. Chelators: CaNa2EDTA, DMSA.
  • Arsenic: Mees' lines (nails), raindrop pigmentation, garlic odor, peripheral neuropathy. Chelators: BAL, DMSA.
  • Mercury: Erethism (mad hatter), tremors, gingivitis (inorganic); Minamata disease (organic). Chelators: DMSA, DMPS.
  • Iron: Necrotizing gastroenteritis, shock, metabolic acidosis in children. Chelator: Deferoxamine.
  • Cadmium: Itai-itai disease (painful bones, osteomalacia), renal tubular dysfunction, emphysema.
  • Thallium: Alopecia (delayed), painful neuropathy (stocking-glove), GI upset. Antidote: Prussian blue.

Practice Questions: Heavy Metal Poisoning

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Buon's line is seen in: Al 07; Rajasthan 11; NEET 13; JIPMER 13

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Flashcards: Heavy Metal Poisoning

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Chronic OP poisoning is usually seen in _____

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Chronic OP poisoning is usually seen in _____

agricultural workers (occupation)

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