Patients with AIP who receive glucocorticoid treatment have significantly higher remission rates of all aspects of clinical, histopathological, and serologic findings than those who do not [20–22]. Glucocorticoid treatment has also been reported to reduce the time to remission and improve the exocrine function of the pancreas. Even though there is no consensus on the indication, steroid treatment for AIP patients can alleviate symptoms and improve radiologic and serologic abnormalities. And steroid therapy should be started when vital organs are affected for preventing severe organ dysfunction and failure. However, not all manifestations of AIP require immediate intervention, and implementation of steroid therapy should be decided based on the significance, functional status, and disease course of the organ affected. In practice, the generally accepted indications of steroid treatment include obstructive jaundice, abdominal pain, back pain, and symptomatic extrapancreatic diseases.

Steroid therapy for AIP consists of induction of remission, withdrawal of steroid, maintenance therapy, and off-steroid therapy (Fig. 22.2). For induction of remission, high dose of steroid is recommended. The exact dose of steroid and duration for remission induction have not been yet established. Most of the experts agree to use 30 mg or 40 mg of prednisolone or prednisone [3, 12, 13, 16, 20, 22–26]. Recently, ICDC defines the starting dose of steroid for induction of remission as 0.6–1 mg/kg per day for type 1 AIP [10]. For the duration of induction of remission with high-dose steroid, the clinical protocols are quite different according to countries. In Korea and Japan, 30–40 mg of oral corticosteroid is usually prescribed for 1–2 months. On the contrary, 40 mg of oral steroid is used for 1 month in the USA. In general, 1 month of 30–40 mg oral corticosteroid can be used as a standard induction of remission regimen. However, the duration of high-dose steroid therapy should be tailored to each patient based on the disease activity of the involved organs.

Before starting withdrawal of steroid, it should be preceded to confirm the responsiveness of disease to the drug. Usually, symptomatic response or remission can be observed within 2–3 weeks after installation of steroid therapy. However, it usually takes several weeks to months to achieve serologic and radiologic remission. Especially, extrapancreatic lesions such as bile duct stricture and retroperitoneal fibrosis take more time to be resolved. The protocols of tapering the steroid after induction of remission are also different from medical center to center. However, most of the protocols taper the drug by 5 mg/week.

The goal of maintenance therapy for AIP is to prevent relapse. Theoretical reasons for need of maintenance therapy are that the relapse rate of AIP has been reported to 30–50 % of all cases. And the serologic and radiologic remissions require more time of treatment in clinical setting. However, the issue of whether maintenance therapy should be used on all patients of AIP or confined to the patients who experienced relapse at least once remains unsolved. Furthermore, the duration of maintenance therapy is another issue to be solved.

Currently, Japanese group and several Korean groups favor the maintenance therapy after induction of remission. Japanese guidelines for AIP suggest maintenance therapy with low dose of steroid (2.5–5 mg/day) should be administered to all patients for 3 years. On the contrary, the US group recommends maintenance therapy only for the patients who experienced relapse. They recommend short course of high-dose steroid therapy for induction of remission and complete withdrawal of steroid by tapering out (5 mg/week).

As already well known, high-dose and long-term steroid treatment increases the risk of adverse effect. In one study, steroid therapy for AIP caused glucose intolerance, exacerbation of preexisting DM, osteoporosis, spinal compression fracture, avascular necrosis of femoral head, and pneumonia [22]. In practice, the change of body shape such as moon face, dorsal hump formation, and weight gain with abdominal striae is the most common side effect during steroid treatment. However, when encountered serious side effects just like osteoporosis with compression fracture, avascular necrosis, and opportunistic infection, steroid therapy should be stopped and other therapy which can spare the requirement of steroid should be considered [22, 24].

The patients of AIP can experience the disease relapse either during withdrawal period or after off-steroid period. Overall rate of relapse in AIP has been 30–50 %. However, these studies have several flaws such as inconsistent definition of relapse, heterogeneity of study population, and incomplete differentiation of subtype. Currently, the relapse is common in type 1 AIP and rare in type 2 disease.