53-year-old woman presents to her GP for a follow-up visit after having high BP on her last visit. She is again found to be hypeensive and was prescribed hydralazine, a b-blocker, and furosemide. The woman takes no additional prescription or over-the-counter medications. She complains of muscle aches, joint pain, and rash. Physical exam reveals a temp. of 37.7degC (100.0degF) and a scaling erythematous rash on her face. The physician orders an autoantibody panel: Antinuclear antibodies (ANA): Positive Anti-histone antibodies: Positive What is the most likely diagnosis?

Rash, ahralgias, and anti-histone antibodies suggest drug-induced systemic lupus erythematosus (SLE). 95% of patients develop ahralgias or myalgias or ahritis in SLE Hydralazine is the causative drug in this case. Positive ANA is nonspecific, as there are many conditions, mostly infectious and autoimmune, that show positive ANA(RIM pattern is specific for SLE). Sensitivity of ANA for drug- induced SLE is 100%, so if ANA is negative, drug-induced SLE can be ruled out. Drugs known to induce SLE- procainamide, chlorpromazine, isoniazid, methyldopa, minocycline, penicillamine, and diltiazem. Drug induced lupus is common in whites and has a less female predilection as compared to SLE Hematological abnormalities, kidney and brain involvement are infrequent and anti-dsDNA antibodies are rarely positive