A 22-year-old receives a blood transfusion and within minutes develops urticaria, bronchospasm, hypotension, and angioedema. His serum IgA levels are undetectable. The mechanism of this severe anaphylactic transfusion reaction in IgA-deficient patients is:
- A Type I IgE-mediated allergy to donor red cell antigens
- B Anti-IgA IgG or IgE antibodies in recipient reacting with IgA in donor blood ✓
- C Complement-activating alloantibodies against donor HLA antigens
- D ABO incompatibility causing intravascular hemolysis
Correct answer: B. Anti-IgA IgG or IgE antibodies in recipient reacting with IgA in donor blood
Explanation
Selective IgA deficiency (most common primary immunodeficiency) carries a unique risk: some IgA-deficient individuals develop class-specific anti-IgA antibodies (IgG or IgE) through sensitization via previous transfusions, pregnancy, or mucosal exposure. When such patients receive blood products containing IgA, the anti-IgA antibodies trigger anaphylaxis. Prevention requires using washed red cells (IgA removed) or blood from IgA-deficient donors. This is distinct from ABO/Rh hemolytic reactions.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
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