Among the autoantibodies detectable in systemic lupus erythematosus, which one has the highest diagnostic specificity for the disease?

• A Antibodies to double-stranded DNA
• B Antibodies to Smith (Sm) antigen ✓
• C Antibodies to Ro/SS-A
• D Anticardiolipin antibodies

Explanation

Anti-Sm antibodies target core proteins of small nuclear ribonucleoprotein particles and are found in only about 20 to 30 percent of SLE patients, but their specificity approaches 99 percent, making them the most specific serological marker. Anti-dsDNA is more sensitive and correlates with nephritis and disease activity, so it is frequently tested but is less specific. Anti-Ro/SS-A also occurs in Sjogren syndrome and neonatal lupus, and anticardiolipin appears in antiphospholipid syndrome and various infections.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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