IgG4-related small-sized occlusive vasculitis in Mikulicz's disease.

Mikulicz's disease is one of the IgG4-related diseases (IgG4-RDs) that involves the cardiovascular system; however, small-sized vasculitis is rare in IgG4-related diseases. A 64-year-old man presented with distal occlusive disease and developed left cerebrovascular infarction with occlusion of the middle cerebral artery and diseased temporal artery branches. He underwent superficial temporal artery-middle cerebral artery anastomosis surgery. Histology of the temporal artery biopsy showed smooth muscle cell proliferation with many IgG4-positive plasma cells. He then developed salivary gland inflammation, and Mikulicz's disease was diagnosed. Small-sized occlusive vasculitis was observed in this IgG4-RD. Low-dose corticosteroid therapy is effective in preventing progressive occlusive disease.