Background/aims To explore and characterise the clinical phenotype of acute anterior uveitis flares with delayed severity in patients with human leucocyte antigen B27 (HLA-B27)-associated anterior uveitis.

Methods Retrospective chart review of patients with HLA-B27-associated anterior uveitis. Demographic and clinical data were recorded, as well as the clinical characteristics of acute anterior uveitis flares. A flare was considered to have delayed severity if any of the following criteria were met within 3–21 days of symptomatic onset: a two-step increase in anterior chamber inflammation on consecutive exams; a new development of hypopyon or fibrinoid aqueous reaction on consecutive examinations or a significant worsening of symptoms.

Results A total of 371 patient charts were identified, of which 137 were included. 321 acute anterior uveitis flares were documented, with 36 (11.2%) meeting the criteria for a delayed severity flare. The average time from symptomatic onset was 10.2 days, and patients presented with an average anterior chamber cell grade of 3.5 in delayed severity flares compared with 1.6 in non-delayed severity flares. No significant difference in frequency of delayed severity presentation was noted based on the presence or absence of systemically associated rheumatological disease, papillitis on initial presentation and retinal vasculitis on initial presentation. The frequency of topical steroid therapy after symptomatic onset was not significantly different between the two flare phenotypes.

Conclusions Our study presents the novel characterisation of a delayed severity phenotype of HLA-B27-associated acute anterior uveitis flares.