Case Report: Acquired Brown Syndrome after COVID-19 Vaccination.

Significance: Brown syndrome, or superior oblique tendon sheath syndrome, is characterized by limitation of elevation on adduction. The disorder is thought to involve the trochlea/superior oblique tendon complex through traumatic, surgical, and inflammatory mechanisms. It could be an indication of multiple underlying immunological or rheumatological disorders.

Purpose: This study aimed to report an unusual strabismus after receiving the first dose of a live attenuated coronavirus disease 2019 (COVID-19) vaccine.

Case Report: A 31-year-old female patient presented with painful vertical diplopia and tenderness of the left trochlear area 3 days after the first dose of COVID-19 vaccination. She had a compensatory chin elevation and face turn to the right, as well as a left 10-prism-diopter hypotropia in the primary position, which increased to 15 prism diopters in the right gaze and disappeared in the left gaze. Ocular motility revealed the limitation of elevation on adduction. The patient denied any history of ocular trauma and was consequently investigated for dysthyroid disease and various immunological and rheumatological disorders, which were excluded. A Hess chart was obtained to document the motility disorder.

Conclusions: We report a case of acquired Brown syndrome in a 31-year-old otherwise healthy woman shortly after COVID-19 vaccination. It is possible that the patient may have developed trochleitis and/or superior oblique tenosynovitis brought on by cross-reacting antibodies generated by the immune response to the vaccine. In the age of the widest vaccination campaign in human history, it is highly likely that we will continue to observe many unexpected potential adverse effects of these vaccines in our clinical practice.