Long Term Prognosis in IgG4-related Systemic Disease (ISD)

IgG4-related Systemic Disease (ISD) is a chronic fibro-inflammatory disorder affecting exocrine and several other organs characterized by the presence of IgG4-positive cellular infiltrates in affected organs and elevated serum IgG4 levels. Autoimmune Pancreatitis (AIP) is the pancreatic manifestation of ISD. Responsiveness to steroid is a characteristic feature ISD and consistently leads to improvement of most lesions including AIP, at least in the short term. However, relapse is common in ISD though there is lack of agreement among different studies on the rates of relapse and factors predicting relapse, with estimates from 25% to upto 50%. Proximal bile duct involvement appears to be predictive of relapse in several studies. Corticosteroids are effective in treating relapses as well and long term maintenance therapy may be necessary in patients who relapse. The role of maintenance of corticosteroid therapy for primary prevention of relapses and utility of immunosuppressive drugs like azathioprine in refractory cases remain to be studied in controlled studies, though there is some experience with successful use of immunosuppressive drugs in refractory cases with frequent relapses. In light of several reports of malignancies, long term follow-up of patients is recommended. Long term survival is currently unknown in ISD due to short-term follow-up and preponderance in older population, and as more follow-up data become available, it will be clear if the consequence of ISD and AIP decreases patient survival.