Introduction Improvement in jaundice and pancreatic enlargement with prednisolone is a reliable and characteristic feature of autoimmune pancreatitis (AIP). The aim of this study was to investigate whether immunosuppression results in long-term preservation of pancreatic structure and function, as this has not been well defined.

Methods We report a single-centre cohort study of all patients diagnosed with AIP from 2004 to 2009. Diagnosis was based on the HISORt criteria, while assessment of pancreatic morphology was made pre and post-treatment, by CT and/or MRI, according to clinical need. Exocrine and endocrine function was measured by stool faecal elastase 1 (FE1) and plasma glucose/HbA1c.

Results Forty-one patients (33M/F8; median age 62 years, range 29–83) were included. Median follow-up to date is 35 months (range 1–71). At diagnosis, a pancreatic mass/diffuse swelling was noted in 36/41 (88%), serum IgG4 was elevated (>1.3 g/l) in 22/41 (54%), and 30/41 (73%) had an immunohistological diagnosis, with >10 IgG4-positive plasma cells/high power field (n=15 pancreas, n=8 liver, n=8 ampulla, n=2 salivary gland, n=2 renal). 30/41 (73%) had IgG4-associated cholangitis, 14/41 (34%) had other organ involvement (n=7 renal, n=3 salivary gland, n=2 retroperitoneal fibrosis, n=2 neurological). Seven (17%) of 41 patients had previously undergone pancreatobiliary surgery for presumed pancreatic cancer (n=3 Whipple resection, n=4 biliary bypass). 38/41 (93%) patients were treated with a tapering oral prednisolone regimen, which was ceased at a median of 6 months (range 2.5–70.9 months). An initial clinical, radiological, and biochemical response was seen in all patients. Relapse following disease remission or failure to wean steroids occurred in 19/41 (46%), and of these patients 6/19 were treated with steroids, and 13/19 were treated with prednisolone 30 mg and azathioprine 2 mg/kg daily. Post-steroid pancreatic atrophy was seen in 23/41 (56%). Low FE1 (<200 μg/g of stool) was noted in 23/41 (56%). 15/41 (37%) patients were diabetic, while 9/41 (22%) have reduced bone mineral density (n=5 osteopaenia, n=4 osteoporosis). Three patients have died during follow-up (n=1 liver failure, n=1 encephalitis, n=1 cholangiocarcinoma).

Conclusion While a favourable initial response to steroids is predictable in patients with a definitive diagnosis of AIP, loss of pancreatic structure and function is common, and the disease is associated with long-term morbidity and mortality. It will be difficult to clearly define the impact of treatment on the outcome of pancreatic and extra-pancreatic disease without a placebo controlled trial.