Serial Changes of Elevated Serum IgG4 Levels in IgG4-related Systemic Disease

Objective Autoimmune pancreatitis (AIP) and Mikulicz's disease have recently been recognized as pancreatic or salivary gland lesions of IgG4-related systemic disease. These are frequently associated with elevated serum IgG4 levels. This study aimed to clarify clinical implications of serial changes of elevated serum IgG4 levels in IgG4-related systemic diseases. Methods Serial changes of elevated serum IgG4 levels were examined in patients with IgG4-related systemic diseases. Patients Serial changes of elevated serum IgG4 levels were examined in 44 patients: AIP (n=24), Mikulicz's disease (n=8), pancreatic cancer (n=5), bile duct cancer (n=1), sclerosing cholangitis (n=1), hypereosinophilic syndrome (n=1), chronic thyroiditis (n=1), hypophysitis (n=1), idiopathic pancreatitis (n=1), and Behcet's disease (n=1). Results The serum IgG4 levels decreased in all patients with AIP and Mikulicz's disease after steroid therapy. The serum IgG4 levels were normalized in 46% of AIP patients and 38% of Mikulicz's disease patients. The serum IgG4 levels were not normalized at remission in 3 of 4 relapsed AIP patients, and re-elevation of serum IgG4 levels was detected in all relapsed patients. Elevated serum IgG4 levels decreased in 3 patients with pancreatic cancer after resection or chemotherapy, and decreased in patients with hypereosinophilic syndrome, sclerosing cholangitis, and hypophysitis after steroid therapy. Conclusion Measurement of serial serum IgG4 levels is useful to determine the disease activity of IgG4-related systemic diseases.