[Malignant lymphoma with IgG4-related disease arising in a very elderly man]

IgG4-related disease (IgG4-RD) which is characterized by an autoimmune abnormality and elevated serum IgG4 level often presents as swelling, nodules, and the thickening of multiple organs. It typically occurs in middle-aged to elderly patients, but its pathogenesis remains unclear. Lymphadenopathy is frequently seen in IgG4-RD, which clinically requires a differential diagnosis from malignant lymphoma. We herein report a case of malignant lymphoma with IgG4-RD arising in a very elderly man.An 85-year old man with a 6-year history of autoimmune pancreatitis was diagnosed as IgG4-related hypophysitis 13 months prior to admission. Hydrocortisone was prescribed for secondary adrenal insufficiency after this presentation. At 9 months before admission, he began to suffer from central diabetes insipidus, and desmopressin was also prescribed at that time. However, 9 months later, he presented with fever, weight loss, and systemic lymphadenopathy while demonstrating elastic hardness, flexibility, and no tenderness. A pathologic specimen obtained from a right axillary lymph node biopsy revealed diffuse large B cell lymphoma. Considering his age and performance status, palliative therapy was chosen, and thus prednisolone was administered. He was transferred to another hospital to receive palliative care on the 55^th day after hospitalization.We should consider the clinical course, pathological findings, serum IgG4 level, and other involved organs in order to differentiate malignant lymphoma from IgG4-related lymphadenopathy. To our knowledge, this case is the oldest known patient to have ever been reported. Both IgG4-RD and malignant lymphoma are frequently seen in elderly people, therefore, we should deepen our knowledge of these diseases.