A Delayed Adverse Reaction: Hydralazine-Induced Lupus After Years of Use.

Drug-induced lupus (DIL) is a rare autoimmune condition triggered by certain medications, most commonly hydralazine and procainamide. DIL can manifest after a few weeks or even after several years of drug exposure. We present a case of a 61-year-old female with hypertension and type 2 diabetes mellitus who developed progressive polyarthritis, myalgia, and fatigue that developed over a year after three years of hydralazine use. Laboratory findings revealed anemia, leukopenia, elevated inflammatory markers, an anti-nuclear antibody (ANA) titer of 1:2560, and anti-histone antibodies of 4.9 units. A false-positive immunoglobulin M (IgM) Lyme antibody complicated the diagnostic workup. Discontinuation of hydralazine and initiation of corticosteroid and methotrexate resulted in resolution after six weeks, confirming the diagnosis of hydralazine-induced lupus.