IgG4-Related Disease

Abstract

IgG4-related disease (IgG4-RD) is a fibro-inflammatory condition characterized by fibrous swelling of affected organs, elevated serum IgG4 concentration in the majority of patients, and a prompt response to corticosteroid therapy. The concept of IgG4-RD as a novel clinical entity emerged at the beginning of the twenty-first century, when Hamano and others noted that, by analogy with sarcoidosis, several seemingly unrelated disorders encompassing a wide range of organs shared common and unique histopathological features. Indeed, many different conditions once regarded as singular entities are now considered part of the IgG4-RD spectrum, such as autoimmune pancreatitis, hypertrophic pachymeningitis, idiopathic retroperitoneal fibrosis, orbital pseudotumor, and Mikulicz’s disease, among others. Vascular involvement has been reported in a proportion of cases of periaortitis and inflammatory aneurysms of the thoracic and abdominal aorta. Given the recent birth of IgG4-RD, little is known with certainty about its immunopathogenesis. A putative pathogenic contribution of the humoral immune response is supported by the rapid clinical responses obtained in these patients with the anti-CD20 monoclonal antibody, rituximab. Novel insights into the pathophysiology of IgG4-RD will likely derive from the identification of possible microbial or self-antigens.