Pathophysiology of Lead Poisoning
Lead poisoning is:
1) excessive levels of lead in tissues
2) most lead in the body is in bones, hair, and teeth where it causes little harm
3) damage occurs with buildup in brain, kidneys, and blood
Signs and Symptoms
Children –
1) irritability
2) drowsiness or hyperactivity
3) ataxia
4) seizures
5) stunted intellectual development
Adult –
6) wrist drop (damage to radial nerve)
7) foot drop (damage to peroneal nerve)
8) paroxysmal adominal pain
9) black deposits in gums
Characteristic Test Findings
Laboratory –
1) microcytic hypochromic anemia
2) basophilic stippling of red blood cells
3) amino acids in urine
4) increased phosphorus in urine
Radiology –
5) lead lines at metaphyseal bone formation sites in children
Histology/Gross Pathology
Children –
1) brain edema (if severe, herniation of uncus and/or cerebellar tonsils)
2) astrocytic proliferation
3) dilation and proliferation of brain capillaries
Adults –
4) damage to proximal tubular cells of kidney with characteristic intranuclear inclusions
Biochemistry
lead inhibits gamma-aminolevulinic acid dehydratase, which causes anemia
Inheritance/Epidemiology
exposure through –
1) ingesting lead-based paint flakes
2) manufacture of automobile batteries
3) lead smelting
4) lead-contaminated moonshine
5) leaded gasoline fumes
Treatment
1) chelating agent EDTA
2) dimercaprol
3) kidney and blood damage is reversible, neurologic damage is permanent
Tips for USMLE
1) if there is no anemia, it can’t be lead poisoning (except from acute massive ingestion such as a 2 year-old eating 10 pencils)
2) main sequelae of lead poisoning – in children, encephalopathy; in adults, peripheral neuropathy
3) if the question mentions basophilic stippling of red blood cells (RBCs), think lead poisoning
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