LAUSR

Objective Idiopathic orbital inflammation (IOI) is a group of orbital inflammatory diseases of unknown etiopathogenesis. We investigated whether patients with IOI have clinical heterogeneity based on the presence (typical group) or absence (atypical group) of a unique onset that periocular inflammatory symptoms emerge suddenly but progress slowly. Methods and analysis This retrospective cohort study included 195 patients diagnosed with IOI. We analysed the clinical data of patients, including the outcomes of corticosteroid treatment, in two subgroups stratified on the basis of the presence (130 patients) or absence (65 patients) of the unique onset. Results Patients in the typical group were significantly younger at disease onset than those in the atypical group (median age; 52 vs 65 years, p=0.002); had more ocular adnexa-specific lesions, namely, dacryoadenitis, myositis, scleritis and optic perineuritis (78% vs 45%, p=0.00001); and had significantly fewer associations with immune-mediated inflammatory diseases (4% vs 15%, p=0.004). Among 30/119 patients (25%) who were steroid refractory in the typical group, a long period of time from symptom onset to initiation of treatment was a significant steroid-refractory risk factor (OR: 16.7), whereas, among the 18/40 patients (45%) who were steroid refractory in the atypical group, intraconal diffuse lesions were a significant steroid-refractory risk factor (OR: 8.8). Conclusion This cohort study suggests clinical heterogeneity between the two subgroups of patients with IOI.