Which laboratory pattern best distinguishes drug-induced lupus from idiopathic systemic lupus erythematosus?

• A High-titre anti-dsDNA antibodies with depressed C3 and C4
• B Anti-histone antibodies with normal complement levels ✓
• C Positive antiphospholipid antibodies with thrombocytopenia
• D Anti-Smith antibodies with a negative ANA

Explanation

Drug-induced lupus, classically caused by hydralazine, procainamide, minocycline and anti-TNF agents, features anti-histone antibodies in over 90% of cases, while anti-dsDNA is rarely positive and complement consumption does not occur. Renal and CNS involvement are distinctly uncommon, and symptoms resolve weeks to months after withdrawal of the offending drug. Option A describes the immunological signature of active idiopathic SLE with nephritis, not the drug-induced form.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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