IgG4-related disease: historical overview and pathology of hematological disorders.

IgG4-related diseases comprise a recently recognized systemic syndrome characterized by mass-forming lesions in mainly exocrine tissue that consist of lymphoplasmacytic infiltrates and sclerosis. There are numerous IgG4-positive plasma cells in the affected tissues, and the serum IgG4 level is increased in these patients. The present study describes the history, autoimmune pancreatitis (AIP), IgG4-related lymphadenopathy and lymphomagenesis based upon ocular adnexal IgG4-related disease. Lymphoplasmacytic sclerosing pancreatitis, a prototypal histological type of AIP, is now recognized as a systemic IgG4-related disease. Lymph node lesions can be subdivided into at least five histological subtypes, and systemic IgG4-related lymphadenopathy should be distinguished from multicentric Castleman's disease. Interleukin-6 and CRP levels are abnormally high in multicentric Castleman's disease, but are normal in the majority of systemic IgG4-related lymphadenopathy. Ocular adnexal IgG4-related disease frequently involves bilateral lacrimal glands swelling, and obliterative phlebitis is rare. Moreover, some malignant lymphomas, especially mucosa-associated lymphoid tissue lymphoma, arise from ocular adnexal IgG4-related disease. In addition, IgG4-producing lymphoma also exists.