Future Perspective

Abstract

The concept of autoimmune pancreatitis (AIP) was first reported in 1995 by Yoshida K et al. [1]. Even before this report, however, cases of AIP or chronic pancreatitis with other organ involvement such as the lacrimal glands, retroperitoneum, and biliary ducts had begun to accumulate in the literature [2–5]. Then in 2001, Hamano et al. [6] reported high serum IgG4 levels in patients with AIP, which is now a hallmark of type 1 AIP/IgG4-related disease (RD). In 2002, Yamamoto Y et al. [7] reported that patients with so-called Mikulicz’s disease, the disease ignored for nearly 50 years [8], also had high serum IgG4 levels. Then, through extensive discussion and communications among experts from different clinical fields, finally, a new concept of IgG4-RD was established by combining AIP, Mikulicz’s disease, and other diseases [9–12]. Since the concept of AIP was introduced in 1995 [1], cases of AIP have been identified not only in Japan but also in other countries, and interesting differences have been observed between AIP cases from Asia and Western countries [13–15]. In brief, AIP in Western countries occurs equally between males and females in a relatively young population and is frequently associated with inflammatory bowel disease. Importantly, no cases had elevated serum IgG4 levels. These features are quite distinct from AIP with high serum IgG4 levels seen in Japan. After extensive discussion, a consensus statement on Asian diagnostic criteria for AIP [16] and international consensus diagnostic criteria (ICDC) for AIP [17] were created, and now, these two types of AIP are referred to as type 1 and type 2 AIP. Diagnosis of type 1 AIP is well established, whereas that of type 2 AIP mainly depends on histological findings, and none of specific serum markers have been identified. Fortunately, both types of AIP generally respond well to corticosteroid treatment. A consensus for treatment of AIP, however, has not yet been established. More importantly, the pathophysiology of AIP is largely unknown.