Autoimmune pancreatitis in the paediatric population - review of the literature and own experience.

Autoimmune pancreatitis (AIP) is a rare chronic inflammatory autoimmune disease of the pancreas. It is estimated that it accounts for 2-6% of all the chronic pancreatitis (CP) cases in adult patients. AIP is usually characterized by sudden onset. The presenting symptoms most commonly include painless jaundice, general weakness and loss of weight. Imaging studies often reveal diffuse enlargement or focal changes of pancreatic parenchyma. In view of the clinical manifestation and changes documented on imaging, AIP should be considered after performing a differential diagnosis from pancreatic cancer or inflammatory masses in the course of CP. According to the International Consensus Diagnostic Criteria (ICDC), AIP can be sub-classified into two subtypes. Type 1 AIP is seen mainly in adult patients and characterized by elevated serum IgG4 levels and its association with IgG4-related disease at extrapancreatic sites (eg, sialadenitis, retroperitoneal fibrosis). Type 2 AIP presents in younger individuals. Serological abnormalities are usually absent. There are no systemic manifestations, except for inflammatory bowel disease. Histologically, type 1 AIP is characterized by massive infiltration by IgG4-positive plasma cells, whereas type 2 AIP shows neutrophilic infiltration with granulocytic epithelial lesions (GELs). Both types rapidly respond to steroid therapy. AIP is extremely rare in children. So far about twenty-five case reports of paediatric AIP were described. Due to such an infrequent occurrence, paediatricians may be unfamiliar with the optimal diagnostic and management strategies of this condition.