A 4-year-old boy living in an old house with peeling paint has abdominal colic, constipation, and a hemoglobin of 7 g/dL. Smear shows hypochromic microcytic cells with coarse basophilic stippling. Lead causes this anemia primarily by:

• A Inducing IgG mediated extravascular hemolysis
• B Direct oxidative damage to the red cell membrane
• C Suppressing erythropoietin production by the kidney
• D Inhibiting ferrochelatase and ALA dehydratase, impairing heme synthesis ✓

Explanation

Lead inhibits delta aminolevulinic acid dehydratase and ferrochelatase, blocking two steps of heme synthesis and creating a sideroblastic state with ringed sideroblasts and basophilic stippling (ribosomal RNA aggregates). Oxidant membrane injury is the mechanism in G6PD deficiency, erythropoietin suppression explains anemia of renal failure, and immune hemolysis occurs in AIHA, none of which produce stippled sideroblastic smears.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.