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Autoimmune pancreatitis: A mimic of pancreatic cancer

Cleveland Clinic Journal of Medicine. 2009 October;76(10):607-615 | 10.3949/ccjm.76a.09039
October 1, 2009|Cleveland Clinic Journal of Medicine
Ryan Law, DO;Mary Bronner, MD;David Vogt, MD;Tyler Stevens, MD
Author and Disclosure Information

Ryan Law, DO
Department of General Internal Medicine, Cleveland Clinic

Mary Bronner, MD
Section Head, Morphologic Molecular Pathology, Pathology and Laboratory Medicine Institute, Cleveland Clinic

David Vogt, MD
Departments of Hepato-pancreatobiliary and Transplant Surgery, General Surgery, and Transplantation Center, Digestive Disease Institute, Cleveland Clinic

Tyler Stevens, MD
Digestive Disease Institute, Cleveland Clinic

Address: Tyler Stevens, MD, Digestive Disease Institute, A31, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195; e-mail stevent@ccf.org

ABSTRACTAutoimmune pancreatitis is an idiopathic inflammatory disease that produces pancreatic masses and ductal strictures. This benign disease resembles pancreatic carcinoma both clinically and radiographically. The diagnosis of autoimmune pancreatitis is challenging to make. However, accurate and timely diagnosis may preempt the misdiagnosis of cancer and decrease the number of unnecessary pancreatic resections.

KEY POINTS

  • Hallmark features of autoimmune pancreatitis include an elevated serum immunoglobulin G4 level, focal or diffuse pancreatic enlargement on imaging, and dense lymphoplasmacytic infiltrates on histologic study.
  • The disease can be associated with extrapancreatic manifestations, including sclerosing cholangitis, sialadenitis and retroperitoneal fibrosis.
  • Autoimmune pancreatitis responds dramatically to corticosteroid treatment.

CORTICOSTEROIDS ARE EFFECTIVE

Our patient’s jaundice temporarily resolved after his biliary bypass operation. If the diagnosis had been made earlier, he could have been treated with corticosteroids.

Corticosteroids have been used to treat autoimmune pancreatitis, with great success. (However, autoimmune pancreatitis occasional resolves spontaneously and stays in remission without corticosteroids.) A common regimen is oral prednisone 40 mg/day for 4 weeks and then tapered by 5 mg every 1 to 2 weeks. Patients who have a delayed response may receive long-term maintenance corticosteroid therapy (2.5–5 mg of oral prednisone).38–40

The radiographic and laboratory abnormalities typically resolve promptly with steroid therapy. A radiographic response is seen as early as 2 to 3 weeks, with normalization occurring in 4 to 6 weeks.40 Serum IgG4 levels decrease concurrently.38

Between 36% and 60% of patients with diabetes and autoimmune pancreatitis have better insulin secretion and glycemic control once corticosteroid therapy is started.3,6,38,40 Fifty percent of patients with exocrine insufficiency have functional improvement after corticosteroid therapy.6

Extrapancreatic lesions also improve with therapy.40,41 Obstructive jaundice may require endoscopic placement of a temporary biliary stent, but after a few weeks of steroid therapy the stent can usually be removed.

The decision to treat with corticosteroids is usually based on symptoms, imaging features (stricture or mass), a low suspicion of cancer (eg, negative biopsy), and an elevated IgG4. A histologic diagnosis of autoimmune pancreatitis is usually not available or required but may be sought through endoscopic ultrasonography-guided core biopsy or laparoscopic biopsy if the diagnosis is in doubt.

Another reasonable approach is an empiric trial of corticosteroids, reassessing the symptoms and repeating the imaging tests after 1 to 2 months. In fact, a response to corticosteroids is a component of most diagnostic criteria (Table 2).

Recurrence rates range from 6% to 32%.4,33,39,42,43 Patients who relapse after initial corticosteroid therapy may be treated again with prednisone in high doses (40 mg/day).38,41 Immunomodulatory therapy has been used successfully to treat relapsed disease in a single reported series: seven patients received either azathioprine (Imuran) 2 mg/kg daily or mycophenolate mofetil (Cell-Cept) 750 mg twice daily, and all remained in complete remission at a median follow-up of 6 months with no adverse events.44

In cases that fail to respond to corticosteroids, the diagnosis of autoimmune pancreatitis should be re-evaluated and surgery should be considered to look for cancer.

CASE CONTINUED

Our patient felt well at his 2-month follow-up visit. However, his serum alkaline phosphatase had increased to 649 U/L, and his serum IgG4 had increased to 980 mg/dL.

Figure 6. In panel A, endoscopic retrograde cholangiopancreatog-raphy (ERCP) prior to corticosteroid therapy shows a high-grade hilar stricture (large arrow) and intrahepatic strictures (small arrows). In panel B, ERCP 6 weeks after corticosteroid therapy shows resolution of the hilar stricture (arrows) and marked improvement in the intrahepatic strictures.
ERCP repeated via the biliary-enteric anastomosis revealed a high-grade hilar stricture and diffuse intrahepatic strictures (Figure 6). Brush cytology from the hilar stricture was negative for malignant cells. Prednisone 40 mg once daily was started to treat presumed biliary involvement of autoimmune pancreatitis.

ERCP repeated 6 weeks later showed that the hilar stricture had completely resolved, and the intrahepatic strictures had markedly improved (Figure 6). His serum alkaline phosphatase level was now 73 U/L, and his serum IgG4 was 231 mg/dL.

Almost 2 years after starting corticosteroid therapy, the patient has remained in good control and the prednisone has been tapered off completely. His latest laboratory values are alkaline phosphatase 70 U/L and IgG4 46 mg/dL.

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