IgG4-related disease presenting as posterior scleritis and vitritis, progressing to multifocal orbital involvement.

IgG4-related disease (IgG4-RD) is a rare, chronic inflammatory condition that may involve nearly every organ system. Originally identified as a cause of autoimmune pancreatitis, its characteristic histological and clinical features have been found in a wide variety of inflammatory presentations, including the eye and orbit. Here we describe an example of a case of IgG4-RD initially presenting as scleritis and vitritis, with further progression to multifocal bilateral orbital involvement. Tissue biopsy of an orbital mass was highly characteristic of IgG4-RD histology and a rapid clinical response to corticosteroids was observed. This case highlights IgG4-RD as a rare cause of intraocular inflammation that may progress to involve the orbit.