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.