Key Clinical MessageLeukocytoclastic vasculitis is a rare, small‐vessel vasculitis that can be caused by sulfamethoxazole‐trimethoprim. Most presentations involve skin rash but serious systemic involvement is possible. The precise mechanism is unclear but genetic and immune‐based tissue damage has been postulated. The rash often resolves with discontinuation of sulfamethoxazole‐trimethoprim with or without steroids.