Aims To evaluate retrospectively the prevalence of positive IgG4-immunostaining in orbital tissue of patients with idiopathic orbital inflammation and to compare the clinical, radiographic and pathologic features among patients with and without IgG4-positive cells.

Patients and methods 25 patients with biopsy-proven idiopathic orbital inflammation examined from January 2006 through December 2011 were included. Immunohistochemistry with IgG and IgG4 immunostaining from biopsy specimens of all patients was performed. Tissue with more than 10 IgG4-positive plasma cells per high-power field and with a ratio of IgG4+/IgG+ plasma cells of more than 40% was scored as positive. Histopathologic features, demographic and clinical data, radiologic findings, treatment and follow-up information for each patient were analysed.

Results Immunohistochemical staining showed 10 cases (40%) were IgG4 positive. The symptoms and signs included eyelid or periocular swelling/mass in all, pain (3/10), extraocular muscle restriction (3/10), proptosis (5/10) and/or decreased vision (4/10). Demographic and clinical findings of these patients did not differ from those with IgG4-negative cells. The presence of positive IgG4-immunostaining in orbital tissue was significantly associated with characteristic pathological features (more background fibrosis, lymphoid hyperplasia, plasma cells and phlebitis).

Conclusions Finally, 40% of patients with biopsy-proven orbital inflammation were classified as IgG4-RD, with typical histological features, but without specific clinical or radiological findings.