Objective: Autoimmune pancreatitis (AIP) is a peculiar type of pancreatitis of presumed autoimmune etiology. However, target antigens for AIP have not been detected. Furthermore, its preponderant occurrence in elderly men and the very dramatic response with no major residual deformity to oral steroid therapy within 2 weeks suggest that the pathogenesis of AIP might not involve autoimmune mechanism. Recently, it was reported that the immune reaction closely involved in the pathogenesis of allergic disorders was upregulated in the affected tissues of AIP. This study aimed to examine the allergic manifestations in AIP patients.
Methods: This case series consisted of 45 AIP patients. Present and/or past histories of allergic diseases, clinical findings, and laboratory data were reviewed.
Results: Twenty patients (allergic-type AIP) had histories of allergic diseases, such as acute allergic rhinitis (n= 11), including rose and hay fever, atopic dermatitis (n= 5), bronchial asthma (n= 3), drug allergy (n= 2), and hypersensitivity pneumonitis (n= 1). Serum IgE levels were elevated in only 12 allergic-type AIP patients, and they were significantly higher in allergic-type AIP patients than in AIP patients without allergic manifestations (P = 0.0001). The peripheral eosinophil count was significantly elevated in allergic-type AIP patients (P =0.048). With respect to initial symptoms, obstructive jaundice was less frequent in allergic-type AIP patients (P = 0.012), and abdominal pain was detected in only five patients with allergic-type AIP (P = 0.013). Allergic-type AIP occurred predominantly from September to February in 19 of 20 patients (P = 0.001).
Conclusion: Allergic manifestations were detected in about half of the AIP patients, and allergic mechanisms may be related to the occurrence of AIP in these patients.