Which laboratory finding best distinguishes drug-induced lupus from idiopathic SLE?
- A High-titre anti-histone antibodies with negative anti-dsDNA ✓
- B Positive anti-dsDNA with low complement
- C Positive anti-Smith antibody
- D Positive lupus anticoagulant
Correct answer: A. High-titre anti-histone antibodies with negative anti-dsDNA
Explanation
Drug-induced lupus, classically caused by procainamide and hydralazine, features homogeneous ANA with high-titre anti-histone antibodies, while anti-dsDNA and anti-Smith are characteristically absent and complement levels remain normal. Renal and CNS involvement are rare. Idiopathic SLE shows the opposite pattern: anti-dsDNA positivity with complement consumption, which is what kills distractor B.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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