IgG4-related lacrimal sac diverticulitis.

IgG4-related disease is characterized by elevated serum IgG4 and tissue infiltration by IgG4-positive plasma cells. We herein report a case of lacrimal sac diverticulitis with marked IgG4-positive plasma cell infiltration. An 89-year-old woman presenting with right lower eyelid mass. Imaging modalities demonstrated a cystic orbital mass located beneath the globe and adjacent to enlarged lacrimal sac. Serological tests showed high IgG4 and normal IgG levels, measuring 242 and 1603 mg/dl, respectively. The orbital mass was surgically excised. Histologically, the excised tissue demonstrated marked inflammation with fibrosis surrounded by mononuclear epithelial cells. A variety of IgG and IgG4-positive plasma cells infiltrated the stroma. This patient was diagnosed as an IgG4-related lacrimal sac diverticulitis, based on current diagnostic criteria of IgG4-related disease. It is likely that IgG4-related inflammation occurs in a lacrimal sac diverticulum, which should be considered a differential diagnosis in inferior orbital tumors.