A case of recurrent IgG4-related disease successfully treated with belimumab after remission of systemic lupus erythematosus

Dear Editor, IgG4-related disease (IgG4-RD) is a chronic systemic disease characterized by the elevation of serum IgG4, infiltration of lymphocytes and IgG4-positive plasma cells, and fibrosis [1]. IgG4-RD affects any organs such as salivary glands, orbits, pancreas, kidneys, aorta, retroperitoneum and mimics malignancy, infection, and other autoimmune diseases including SLE. SLE is also a chronic inflammatory disease that presents variable symptoms, and IgG4-RD and SLE rarely coexist. The first-line treatment of IgG4-RD is glucocorticoids (GCs). Although IgG4-RD usually shows a good response to GCs, it often relapses. When GC treatment fails, there is no evidence on what immunosuppressive agents should be added next. We herein report a case of IgG4-RD complicated with SLE, successfully treated with belimumab for the relapse of IgG4-RD, not SLE, possibly leading to novel insights into the treatment of IgG4-RD. A 76-year-old man with fatigue and 4 kg weight loss was admitted to...