To report a case of IgG4-related sclerosing dacryoadenitis masquerading for a long period as a.

A 59-year-old man with visual acuity loss and proptosis in the left eye was referred to our hospital. Ten years prior, the patient was diagnosed with lymphoma and underwent chemotherapy at another hospital. However, the patient spontaneously stopped treatment and took steroids for the relief of periorbital swelling. Magnetic resonance imaging revealed diffuse infiltrative lesions involving both optic nerves and extraocular muscles. Incisional biopsies of the lacrimal gland's posterior side and the lateral rectus muscle's lateral side were performed. Staining for IgG4 via immunochemistry showed infiltration of IgG4-positive lymphoplasmacytic cells. Under the diagnosis of IgG4-related sclerosing disease, the patient underwent high-dose steroid pulse therapy.