Bilateral pseudotumoral proptosis as presenting sign of orbital hyper-IgG4-related disease

Hyper-IgG4 syndrome is a rare cause of bilateral proptosis. It must always be considered after ruling out orbital lymphoma. We report a case of progressive bilateral proptosis for 4 years in a 34-year-old man. Orbital MRI showed an infiltrative process extending to the orbital fat, extraocular muscles and lacrimal glands. Lacrimal gland biopsy with immunohistochemical study showed a lymphoplasmocytic infiltrate rich in IgG4 and fibrosis. The diagnosis of orbital hyper-IgG4 syndrome was suggested. The patient responded well to systemic steroid treatment. Orbital hyper-IgG4 syndrome manifests most often as pseudo-tumoral bilateral proptosis. Elevated IgG4 levels are neither sensitive nor specific. Biopsy with immunohistochemical study is the key to diagnosis. Systemic steroid treatment is the gold standard, but recurrences may occur.