[Retroperitoneal fibrosis and Castleman disease in two patients with high IgG4 levels].

With the cumulative increase in the number of autoimmune pancreatitis cases, the disease is now widely accepted as a symptom of IgG4-related systemic disease. We recently experienced two cases of retroperitoneal fibrosis and Castleman disease presenting high IgG4 levels without evident pancreatic lesions. Both patients were successfully treated with steroid therapy. It is necessary to acknowledge that retroperitoneal fibrosis and Castleman disease, with or without pancreatic lesions, may have aspects of IgG4-related systemic disease and that the measurement of serum IgG4 and tissue immunostaining for IgG4 should be considered for diagnosing and treating the conditions.