Background: In 50–63% of the cases autoimmune pancreatitis (AIP) is associated with autoimmune diseases (AID), suggesting that it may be a systemic disorder. The aim of the present study was to investigate the coexistence of AIP and an elevated serum IgG4 level in AID. Methods: The serum level of IgG4 was measured in 61 patients with AID of different types who had not yet participated in steroid treatment. Abdominal ultrasonography (US) and in some cases computer tomography (CT) were performed in patients with an elevated IgG4 level. Results: Elevated serum IgG4 levels (919±996mg/l) were detected in 17 of the 61 AID patients (28%). 10 of the 17 had Sjögren's syndrome (IgG4: 590±232mg/l), 2 of them in association with Hashimoto's thyroiditis. The remains 7 patients (IgG4: 1388±985.5mg/l) were diagnosed with systemic lupus erythematosus (SLE), in 1 of them was accompanied by Raynaud's syndrome. The highest IgG4 level (3815mg/l) was detected in this patient. The serum IgG4 level was elevated in 83% (5 of the 6 cases) of the AIP patients (783±522mg/l). This IgG4 value was significantly lower than that in the SLE patients, but not significantly different from that in patients with Sjögren's syndrome. Abdominal US and CT did not reveal any characteristic features of AIP among the AID patients with elevated IgG4. Conclusions: The serum IgG4 level is often elevated in AID, but an elevated IgG4 level was not diagnostic of AIP in this group of patients. This work was partly supported by the TÁMOP-4.2.1./B- 09/1/KONV.
