Lead poisoning

Last revised by David Carroll on 3 Dec 2022

Lead poisoning or plumbism refers to the multi-organ toxicity exerted by exposure to lead. Manifestations differ based on a myriad of features including chronicity, exposure intensity, and age. Neurologic toxicity and hematologic toxicity are common features. Clinical manifestations vary, ranging from mild (or asymptomatic) cases to a severe life-threatening encephalopathy 6.

Common sources of exposure to this ubiquitous metal may be broadly classified as occupational (or recreational), environmental, or perinatal (primarily trans-placental). Environmental sources may include 6:

  • lead-based paint

    • structural renovation (e.g. sanding) or senescence (e.g. flaking) results in incorporation in soil and/or dust contamination

    • most common source of pediatric exposure

  • contamination of food or water

    • degradation of lead-containing pipes and solder in plumbing

    • cans may contain lead solder

    • contamination of illegally distilled alcohol ("moonshine"), cooking spices, traditional remedies

Sources of occupational and recreational exposures include:

  • lead smelting, metal work (e.g. welding)

  • automobile work (especially related to radiators)

  • firearm ranges

  • construction workers, painters

Presenting features vary as a function of factors such as age (pediatric predisposition to more severe neurologic toxicity), ingested dose, and chronicity of exposure.

  • neurologic

    • milder pediatric cases may manifest with disturbances in behavior, growth, hearing and cognition

    • severe pediatric cases may progress to encephalopathy with seizures, coma, ataxia, cerebral edema

    • adults may similarly demonstrate mild (tired, irritable) symptoms or a severe encephalopathy

      • peripheral motor neuropathy may also develop

  • gastrointestinal

  • hematologic

    • anemia

      • hemolysis may also be observed

      • elevations (chronic) in zinc and erythrocyte protoporphyrin

  • reproductive

    • miscarriages

    • infertility

      • may impair spermatic function and spermatogenesis

  • renal

  • cardiovascular

    • hypertension

  • musculoskeletal

    • gout

  • bones

    • bone remodeling and growth may be affected in pediatric cases, with proposed mechanisms including 10

      • alterations in circulating endocrine factors such as parathyroid hormone and activated vitamin D

      • derangement in paracrine signaling factors such as osteocalcin

      • direct cellular toxicity, particularly affecting osteoclasts

    • growth trajectory and height may be affected

    • pathologically increased deposition of calcium in the zones of provisional calcification responsible for the dense metaphyseal bands on radiographs referred to as "lead lines"

  • anemia is multifactorial

    • multi-step inhibition in heme synthesis

      • including aminolevulinic acid dehydratase and ferrochelatase 9

    • may impair production of erythropoeitin 6

    • erythrocyte functional and structural derangements

      • inhibition of erythrocyte sodium-potassium pump 8

        • predisposing to breakdown of the cell membrane and hemolysis

      • inhibition of pyrimidine 5' nucleotidase

        • residual nucleotide clumps in cytosol appear as basophilic stippling

  • may show bands of increased density at the metaphyses

  • can affect any metaphysis, but the involvement of the proximal fibula and distal ulnar metaphyses is highly suggestive

  • may show bone-in-bone appearance

  • abdominal radiographs utile for identification of exposure source and anatomic location if an ingestion is suspected 7

    • intra-luminal radio-opaque foreign body (or multiple punctate densities)

    • serial radiographs may be used to monitor effectiveness of bowel decontamination

  • identification of source crucial to prevent ongoing toxicity 6

  • meticulous supportive care

  • decontamination of ongoing sources of enteral absorption (paint chips, foreign bodies)

    • endoscopic retrieval

    • whole bowel irrigation

  • some patients may require chelating agents to enhance elimination

    • dimercaprol

      • also known as "British anti-Lewisite" or BAL

    • dimercaptosuccinic acid (DMSA)

      • also known as succimer, the favored available oral chelating agent over d-penicillamine

    • edetate calcium disodium (CaNa2EDTA)

Lead has been used extensively since ~7000 BCE 5. Its chemical symbol Pb, is short for plumbum, the Latin word for lead. This is the origin of the word plumber and plumbing as lead has been widely used for water pipes in the home since Roman times, and also 'plumbism', a synonym for lead poisoning 5

  • healed rickets

  • physiological appearances in <3 years' age group

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