A Case of IgG4-Related Disease With Sinonasal Involvement Presenting With Decreased Visual Acuity.

IgG4-related disease (IgG4-RD) is a systemic inflammatory disease characterized by IgG4-positive plasma cell and T lymphocyte infiltration of multiple organs. It commonly involves the pancreas, lacrimal glands, and salivary glands, and it has been rarely reported in the sinonasal cavity. We herein report the case of a 47-year-old male patient whose chief complaint was decreased visual acuity. A tumefactive mass was found on imaging studies, originating from the sinonasal cavity and invading the orbit, kidney, and meninges. The mass was resected through endoscopic sinus surgery and was pathologically confirmed to be IgG4-RD. The patient was treated with steroid therapy and showed clinical improvement.