A Successful Outcome of Upadacitinib Therapy in a Patient with Genital Erosive Fixed Drug Eruption: A Case Report.

Fixed drug eruption (FDE) is a common cutaneous adverse drug reaction with limited effective treatments for severe genital erosive cases. This first reported case demonstrates the successful use of the selective Janus kinase 1 (JAK1) inhibitor upadacitinib as monotherapy for a severe, erosive FDE involving the genitalia. A 50-year-old male presented with rapidly progressing, painful erythema, erosions, and exudation on the scrotum and glans penis following drug intake, confirmed by histopathology. Treated solely with upadacitinib, the lesions achieved near-complete re-epithelialization by day 18, with no recurrence or adverse events during follow-up. This case highlights upadacitinib as a rapidly effective and well-tolerated novel therapeutic option for severe FDE in sensitive areas, addressing an unmet need and expanding the potential application of targeted Janus kinase (JAK) inhibition in cutaneous adverse drug reactions.