IgG4-related lymphadenopathy and IgG4-related lymphoma: moving targets

IgG4 is the least common of all the IgG subclasses. In recent years an uncommon systemic disease characterized by variable manifestations that may include the presence of tumour-like sclerosing lesions in a variety of extranodal sites, lymphadenopathy, presence of increased numbers of IgG4+ plasma cells in affected tissues, elevated serum IgG4 level, frequent presence of autoantibodies and often, a good response to steroid therapy or Rituximab has been described. The disorder has been called IgG4-related sclerosing disease, IgG4-related systemic disease and IgG4-related autoimmune disease; currently the preferred designation is IgG4-related disease (IgG4-RD). In addition to other changes that may be found in association with IgG4-RD, some investigators have suggested that IgG4-RD may serve as a substrate for the development of lymphoma.This review focuses on lymphadenopathy associated with IgG4-RD and also explores the significance of isolated lymphadenopathy with increased numbers of IgG4+ plasma cells. Emerging data on lymphomas arising in association with IgG4-RD and the possibility of an increased risk of lymphoma in patients with IgG4-RD are also discussed.