The importance of IgG4 in the predictive model of thyroiditis

Summary Immunoglobulin (Ig)G4-related sclerosing disease (IgG4-RSD) is a new disease entity first proposed with regard to autoimmune pancreatitis. A 67-year-old male patient was examined because of weight loss and an abdominal pain. Based on the clinical characteristics, laboratory parameters and ultrasound features, we identified the diagnosis of the IgG4-related systemic disease (IgG4-RSD), that was confirmed by the histopathological analysis after the biopsy of the head of pancreas. After confirmation, we started with the corticosteroid therapy with a good clinical, biochemical and morphological response. During the previous therapy, the disturbance of glucoregulation appeared, so we had to change the modality of treatment. We decided to add Azathioprine to the therapy in a dose of 150 mg/day. We achieved a stable phase of the disease with IgG 4.37 g/l and IgG4 0.179 g/l, and with no side effects from the therapy. Learning points There are potential clinical applications of identifying subsets of patients with IgG4 thyroiditis (FVHT and Riedel thyroiditis). A trial of immunosuppressive therapy should be included if a resection is deemed inadvisable. In particular, cases of FVHT that mimic malignancy, tissue and serum IgG4 may provide supportive diagnostic information.