Purpose: To describe an unusual case of frosted branch angiitis that developed in a patient with acute onset systemic vasculitis possibly triggered by the antithyroid medication methimazole.
Methods: We conducted a thorough review of the medical records of a 16-year-old female patient who presented with frosted branch angiitis. During the initial hospital admission, the patient underwent an extensive systemic workup to determine the etiology of her disease and ophthalmologic testing including fundus photographs and fluorescein angiography.
Results: Our patient presented with a unilateral acute onset loss of vision, whose fundus examination revealed the pathognomonic features of frosted branch angiitis. Extensive systemic workup revealed an antineutrophilic cytoplasmic antibody-positive vasculitis, possibly triggered by methimazole.
Conclusion: This case is the first reported frosted branch angiitis associated with a drug-induced antineutrophilic cytoplasmic antibody-positive vasculitis triggered by methimazole.