Drug-Induced Lupus: A Forgotten Cause of Prolonged Pyrexia of Unknown Origin

The causes of a pyrexia of unknown origin (PUO) are broadly spread across infectious, malignant, or inflammatory conditions. The authors report a case of a 43-year-old female who initially presented with hypoxia and fevers secondary to a presumed acute viral or bacterial infectious pulmonary insult. However, fevers persisted despite pulmonary imaging remaining normal. The case subsequently evolved into a PUO with multiple lines of investigation proving inconclusive. No definitive diagnosis was made at the time of discharge; however, cessation of hydralazine was noted to coincide with the last of the patient’s fevers. Following the discharge, her anti-histone antibodies returned a positive result, and the diagnosis of drug-induced lupus was made with hydralazine as the presumed trigger.