IgG4 related orbit disease - An unusual cause of an orbital mass.

IgG4-related disease is a newly described systemic autoimmune and allergic disease, characterized histologically by a fibroinflammatory response with IgG4 plasma cells. It was initially described as affecting the pancreas, but commonly involves the head and neck region as well. While a biopsy is essential for definitive diagnosis, cross sectional imaging may be the initial modality which may suggest this entity. We describe a case of pathologically proven IgG4 related disease which highlights some key radiologic features seen in this entity. Our case highlights some key radiological features of IgG4- related disease in the head and neck, with involvement of the lacrimal glands, pituitary gland and cranial nerves on CT.