A 10-year-old boy develops fever, generalized lymphadenopathy, arthralgias, and glomerulonephritis 10 days after receiving antivenom for a snake bite. Which mechanism underlies this condition?

• A Cross-linking of IgE on mast cells
• B Cytotoxic IgG antibodies against cell surfaces
• C Activation of CD8+ cytotoxic T lymphocytes
• D Deposition of circulating immune complexes in vessels and glomeruli ✓

Explanation

This is a classic presentation of serum sickness, a systemic Type III hypersensitivity reaction. It occurs 7-14 days after exposure to a large amount of foreign antigen, leading to formation of circulating immune complexes that deposit in vessels, joints, and glomeruli, activating complement. The Arthus reaction is a localized form of Type III.

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.