Background: Hypocomplementemic urticarial vasculitis (HUV) has been defined as a syndrome associated with urticarial lesions caused by leukocytoclastic vasculitis. It has been observed in patients with systemic lupus erythematosus and related conditions. Immunoglobulin G4 (IgG4)-related disease is a lymphoproliferative disorder characterized by sclerosing pancreatitis, retroperitoneal fibrosis, sclerotic cholangitis, acute interstitial nephritis, and Mikulicz's disease, and associated with elevated levels of IgG4 and hypocomplementemia. Various cutaneous lesions may occur in IgG4-related disease. Methods: We report a 74-year-old woman with HUV, followed by systemic organ involvement suggestive of IgG4-related disease. Symptoms included submandibular gland swelling, lymphadenopathy, interstitial nephritis, and a thyroid nodule. Laboratory examinations revealed an elevated serum IgG4 level of 637 mg/dl in a total IgG level of 2176 mg/dl, and the production of autoantibodies such as rheumatoid factor and antiphospholipid antibodies. In the swollen lymph node, neither clonal proliferation of T or B cells nor Epstein-Barr virus infection was detected, although the structure had been destroyed by the infiltration of lymphocytes and plasma cells. Among total IgG-producing cells, approximately 40% were positive for IgG4. Results: All symptoms and abnormal laboratory findings improved in response to oral prednisolone. Conclusions: Hypocomplementemic urticarial vasculitis may represent a clinical symptom of IgG4-related disease.
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