Hydralazine-induced lupus without kidney involvement
A 45-year-old woman with stage 3 CKD has had hypertension well controlled for 3 years on lisinopril, chlorthalidone, and hydralazine. She reports 4 months of malaise, low-grade fevers, and arthralgias. Temperature is 38.2°C. She has diffuse muscle tenderness without joint swelling and a faint maculopapular rash on her arms and torso. Creatinine is 1.4 mg/dL (1.6 two years ago); C3 120 and C4 39 mg/dL; ANA <1:80 (≤1:40); anti-dsDNA 0 IU/mL; anti-histone antibodies 1:32 (<1:16); MPO-ANCA 3 U (<1); PR3-ANCA 0.3 U (<1). Urinalysis is negative for protein and blood. What is the best next step?