IgG4-Related Disease

IgG4-related disease (IgG4-RD) is known as an IgG4-related systemic disease, hyper-IgG4 disease, IgG4-related autoimmune disease, IgG4-associated disease, IgG4-related sclerosing disease, and IgG4-syndrome. It is a multi-organ, fibro-inflammatory condition with tumefactive lesions of unknown etiology and characteristic histopathological features. Virtually any organ can be involved, but the most commonly involved organs are the pancreas, kidneys, orbital adnexal structures, salivary glands, and retroperitoneum. The pathological hallmark of this disease is dense lymphoplasmacytic infiltrate with IgG4 positive plasma cells, storiform fibrosis, obliterative phlebitis, and a variable amount of eosinophils. Elevated levels of serum IgG4 is frequent. The pathology is very specific and looks similar in all organs. Because of this finding, it is considered to be analogous to systemic sarcoidosis. IgG4-RD affected patients are often misdiagnosed as having a malignancy since the lesions can mimic tumors, infections, or immune-mediated diseases. This is because of the lack of a systemic approach, and hence, this disease is underdiagnosed. These patients usually have a good recovery after being treated with systemic glucocorticosteroids. The response to steroids is so dramatic that it is has been suggested as one diagnostic criterion for the disease.