IgG4-Related Disease (IgG4+MOLPS) - Diagnostic Criteria and Diagnostic Problems

Since the first report on patients with elevated serum IgG4 in sclerosing pancreatitis in 2001, various systemic disorders, described by many names, have been reported. Despite similarities in the organs involved in IgG4-related Mikulicz's disease and Sjogren's syndrome, there are marked clinical and pathological differences between the two conditions. On the other hand, differential diagnosis of IgG4-related Mikulicz's disease and Kuttner's tumor is very difficult, since their pathological features are closely related except severe fibrosis. Most patients diagnosed with autoimmune pancreatitis in Japan have IgG4-related sclerosing pancreatitis, a disease distinct from the western type. It is likely that patients formerly diagnosed with Castleman's disease with good response to glucocorticoid treatment may have had IgG4-related lymphadenopathy, and should be re-assessed in light of recent findings. Diagnosis of IgG4-related disease is characterized by both 1) elevated serum IgG4 (>135 mg/dl) and 2) histopathological features including lymphocyte and IgG4+ plasma cell infiltration (IgG4+ plasma cells/IgG+plasma cells >40% on a highly-magnified slide checked at five points). Differential diagnosis from other distinct disorders, such as sarcoidosis, Castleman's disease, Wegener's granulomatosis, lymphoma, cancer, and other existing conditions that show the high serum IgG4 level or abundant IgG4-bearing plasma cells in tissues is necessary.