Aim To determine the proportion of idiopathic orbital inflammation (IOI) and orbital benign lymphoid hyperplasia (OBLH) accounted for by immunoglobulin (Ig)G4-related orbital disease (IgG4-ROD) using the comprehensive diagnostic criteria for IgG4-related disease published by Umehara et al and the consensus diagnostic criteria published by Deshpande et al. Secondary aims were to compare the histological and clinical features of IgG4-ROD and non-IgG4-ROD cases, and to compare IgG4-ROD cases diagnosed using the comprehensive diagnostic criteria with those diagnosed using the consensus diagnostic criteria.

Methods A retrospective histopathological review and clinical case series. 55 cases of biopsy-confirmed non-granulomatous IOI and 10 cases of biopsy-confirmed OBLH were included. The intensity of sclerosis, lymphoplasmacytic infiltration and eosinophilic infiltration was graded from 0 to 3+ using a standardised and validated scoring system.

Results IgG4-ROD accounted for 50% and 40% of cases originally diagnosed as OBLH and 23.6% and 5.4% of cases originally diagnosed as IOI, using the comprehensive diagnostic criteria and the consensus diagnostic criteria, respectively. IgG4-ROD cases had numerous significant histological differences, but relatively few significant clinical differences, from non-IgG4-ROD cases. Compared with the comprehensive diagnostic criteria, the consensus diagnostic criteria identified a group of IgG4-ROD cases with a slightly higher ratio of IgG4+ to IgG+ (p=0.01) and a slightly longer duration of symptoms (p=0.02).

Conclusions This is the largest review of IgG4 staining among biopsy-confirmed IOI and OBLH. IgG4-ROD accounted for a substantial proportion of OBLH. The prevalence among cases of IOI was considerably reduced when the consensus diagnostic criteria were used in place of the comprehensive diagnostic criteria.