A 12-year-old boy develops migratory polyarthritis and carditis 3 weeks after an untreated group A streptococcal pharyngitis. The molecular mimicry hypothesis for acute rheumatic fever proposes that streptococcal antibodies cross-react with which human tissue antigen?

• A Cardiac myosin and valvular endothelium ✓
• B Glomerular basement membrane type IV collagen
• C Synovial joint urate crystals
• D Skeletal muscle acetylcholine receptors

Explanation

In rheumatic fever, antibodies against group B streptococcal M protein cross-react with cardiac myosin and valvular tissues (Type II hypersensitivity), causing pancarditis and valvular damage. Option B describes Goodpasture syndrome. Option C describes gout. Option D describes myasthenia gravis. The molecular mimicry between streptococcal antigens and heart tissue is the central pathogenic mechanism.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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