IgG4-related disease with pseudotumor formation in the larynx.

Mikulicz's disease, an immunoglobulin G4-related disease (IgG4-RD) occurs frequently in the head and neck region but rarely in the larynx. We report a case of IgG4-RD with pseudotumor formation in the larynx. A 50-year-old man presented at our facility for a complete physical examination and diagnostic testing of a left arytenoid tumor. On examination, a large supraglottic mass was noted with signs of dyspnea. Movement disorder of the vocal fold was absent. The patient underwent surgery with general anesthesia to improve respiratory symptoms and a resected specimen was submitted for diagnosis. The pathology findings revealed lymph follicle formation, interstitial follicular fibrosis, angiogenesis, and inflammatory cell infiltration with plasmacytosis. Immunohistologic staining at high magnification revealed one hundred or more IgG4-positive plasma cells and fifty percent IgG4/IgG. In addition, obliterative phlebitis was observed. Medical history was positive for retroperitoneal fibrosis with serum IgG4 levels below the diagnostic criteria of IgG4-RD, but histological characteristics of IgG4-RD were met. The diagnosis of IgG4-RD was established, oral treatment with prednisolone (0.6 mg/kg/day) was initiated, and the tumor reduced in size. IgG4-RD may cause irreversible functional impairment. Early diagnosis and treatment are important in reducing the risk of permanent impairment of vocal fold mobility.