A 38-year-old woman presents with polyarthritis of the wrists and MCP joints, photosensitivity, oral ulcers, and a positive ANA at 1:320 (speckled pattern). She has been taking procainamide for 8 months for a cardiac arrhythmoid. Anti-histone antibodies are positive. Anti-dsDNA, anti-Smith, and complement levels are normal. Which of the following is the most likely diagnosis?
- A Drug-induced lupus erythematosus ✓
- B Systemic lupus erythematosus
- C Mixed connective tissue disease
- D Undifferentiated connective tissue disease
Correct answer: A. Drug-induced lupus erythematosus
Explanation
Drug-induced lupus characteristically presents with arthritis, serositis, and constitutional symptoms but rarely involves kidneys or CNS. Anti-histone antibodies are present in over 95% of cases (especially with procainamide, hydralazine, isoniazid). Anti-dsDNA is usually negative, unlike idiopathic SLE where it is a hallmark. Procainamide is among the highest-risk drugs. Symptoms typically resolve upon drug withdrawal.
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.