A Case of Relapsed IgG4-Related Disease Manifested as Mastitis after Treatment of a Submandibular Gland Lesion

Abstract

Immunoglobulin (Ig) G4-related disease is a chronic inflammatory disease characterized by high serum IgG4 levels and formation of a mass, nodule, or hypertrophic lesion in organs caused by infiltration of IgG4-positive plasma cells and fibrosis ; such type of disease is rarely found in the mammary glands. We report a case of a patient with relapsed IgG4-related disease manifested as mastitis after being treated for a submandibular gland lesion. A 51-year-old woman, who had a history of bilateral submandibular gland swelling 30 months before visiting our department, was diagnosed with IgG4-related disease based on submandibular gland biopsy findings. Her symptoms improved after 22 months of treatment with steroids. Five months after termination of the treatment, the patient noticed a mass in her left breast and visited our department once again. Breast ultrasonography revealed clustered microcysts with blood flow in the left CD region. Considering the possibility of malignancy, a needle biopsy was performed, which showed high levels of infiltration of lymphocytes and plasma cells. Immunostaining showed an IgG4/IgG ratio of 80-90% and >10/HPF of IgG4-positive plasma cells. Based on these findings, IgG4-related mastitis was diagnosed and steroid treatment was resumed.