Introduction

Recently, autoimmune pancreatitis (AIP) has been accepted worldwide as a unique, distinctive disease, in which histopathological findings show abundant infiltration of IgG4-positive plasma cells and fibrosis, known as lymphoplasmacytic sclerosing pancreatitis (LPSP), and clinical manifestations that dramatically respond to steroid therapy. In addition to pancreatic lesions, patients with AIP have occasional extrapancreatic lesions such as sclerosing cholangitis (SC), sclerosing sialoadenitis, and retroperitoneal fibrosis similar to LPSP. Among the extrapancreatic lesions, the bile duct is the most commonly involved organ, manifesting as a sclerosing cholangitis which results in obstructive jaundice. AIP is recognized as the pancreatic manifestation of a novel systemic disease referred to as IgG4-related sclerosing disease [1].

IgG4-related sclerosing cholangitis (IgG4-SC) is a recently recognized disease entity characterized by microscopic findings of sclerosing inflammation with an infiltration of abundant IgG4-positive plasma cells, and AIP is associated in most cases. Before establishing the concept of AIP, IgG4-SC used to be misdiagnosed as primary sclerosing cholangitis (PSC) complicating chronic pancreatitis. Therefore, differential diagnosis between IgG4-SC and PSC is important. The cholangiographic findings in IgG4-SC and PSC are similar [2, 3]. Elevation of serum IgG4 is frequently observed in patients with IgG4-SC, which responds dramatically to steroid therapy [4]. In contrast, even if the patients with PSC are medicated, it remains a progressive disease that involves the intra- and extra-hepatic bile ducts and leads to biliary cirrhosis. The effects of steroid therapy for PSC have been reported to be skeptical [5, 6] and liver transplantation is the only effective therapy. Histopathologically, lymphoplasmacytic and eosinophilic infiltration with mild fibrosis are seen in both IgG4-SC and PSC; and recent studies based on immunohistochemical findings of liver biopsy specimens report that IgG4-positive plasma cell infiltration is significantly more severe in IgG4-SC than in PSC [4, 7–11]. However, herein, we report 3 cases of PSC with an infiltration of abundant IgG4-positive plasma cells and ineffective steroid therapy.

Case report

Case 1

A 32-year-old man with elevated serum levels of hepato-biliary enzymes was admitted to our hospital. At the age of 22 years, the patient was diagnosed as PSC in other hospitals, and he had been treated with ursodeoxycholic acid. At the age of 24 years, he was found to have ulcerative colitis (UC). Physical examination at the time of admission revealed no significant findings except for jaundice. Laboratory examinations showed the following values (normal range): peripheral white cell count, 5700/μl (3500–8500); peripheral eosinocyte count, 251/μl (18–510); C-reactive protein, 1.1 mg/dl (<0.3); total bilirubin, 10.9 mg/dl (0.2–1.2); alkaline phosphatase, 2929 U/l (107–340); γ-glutamyl transpeptidase, 413 U/l (11–64); asparate aminotransferase, 133 U/l (13–35); alanine aminotransferase, 192 U/l (5–35); amylase, 127 U/l (37–125). Hepatitis B surface antigen and antibody to hepatitis C virus were negative. Serum IgG, IgG4, IgA, and IgM levels were 2104 mg/dl (870–1700), 96 mg/dl (4.8–105), 291 mg/dl (110–410), and 157 mg/dl (33–190), respectively. Rheumatoid factor was negative. Antinuclear antibody was positive. Among tumor markers, CEA was 1.8 ng/ml (<5.0) and CA19-9 was 237.2 U/ml (<37). Magnetic resonance cholangiopancreatography (MRCP) and endoscopic retrograde cholangiopancreatography (ERCP) revealed strictures of both the hepatic hilar region and the distal common bile duct and no narrowing of the main pancreatic duct (Fig. 1a, b). Cytology of bile juice was negative for malignancy. Histopathological examination by liver biopsy showed moderate lymphoplasmacytic and eosinophil infiltration with fibrosis in the enlarged portal area (Fig. 1c). Duct and ductular proliferation was conspicuous. Fibrous cholangitis (onion-skin fibrosis) was observed. These findings were compatible with PSC. The numbers of immunohistochemically identified IgG4-positive plasma cells were counted under five different high-power fields (hpf). Immunostaining study showed typical inflammation with abundant IgG4-positive plasma cells (126 cells/hpf) (Fig. 1d), a characteristic finding in IgG4-SC. His liver dysfunction was serious, with progressive ascites and jaundice, therefore it was determined that liver transplantation might be necessary.

Although oral steroid therapy requires a long period for drug tapering, steroid pulse therapy is a well-recognized alternative for refractory autoimmune pancreatitis without steroid tapering, as previously reported [12]. Therefore, we twice administrated steroid pulse therapy with 500 mg/day of methylprednisolone for 3 days/week. The hepato-biliary enzymes improved a little after steroid therapy, but MRCP revealed no improvements of strictures of the hilar and distal common bile ducts. Therefore, we strongly suspected PSC. Two months later, we decided on liver transplantation with consent of the patient and his family. Histopathological findings of the liver after transplantation showed severe lymphoplasmacytic and eosinophil infiltration with fibrosis in the enlarged portal area (Fig. 2a, b). Duct and ductular proliferation was conspicuous, and onion-skin fibrosis was observed, which suggested typical advanced PSC findings. Histopathological findings of the pancreas biopsy during the operation showed infiltration of mononuclear cells around the pancreatic duct (Fig. 2c) with an infiltration of abundant IgG4-positive plasma cells (Fig. 2d), but did not show LPSP.

Fig. 1
figure 1

ERCP images and histopathological findings of case 1 on clinical onset. ERCP revealed strictures of the hepatic hilar area (a) and the distal common bile duct, and no narrowing of the main pancreatic duct (b). Histopathological findings of the liver biopsy showed a moderate lymphoplasmacytic and eosinophil infiltration with fibrosis, and fibrous cholangitis (onion-skin fibrosis) (H&E staining ×200, c). IgG4-immunostaining of the liver biopsy showed infiltration of abundant IgG4-positive plasma cells (×200, d)

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Fig. 2
figure 2

Histopathological findings of case 1 on transplantation. Histopathological findings of liver after transplantation showed severe lymphoplasmacytic and eosinophil infiltration with fibrosis in the enlarged portal area (H&E staining ×100, a; ×400, b). Duct and ductular proliferation was conspicuous, and onion-skin fibrosis was observed. Histopathological findings of the pancreas biopsy during operation showed that infiltration of mononuclear cells around pancreatic duct (H&E staining ×200, c). IgG4-immunostaining of the pancreas biopsy during operation showed infiltration of abundant IgG4-positive plasma cells (×200, d)

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Case 2

A 74-year-old woman was admitted to our hospital with liver dysfunction. Laboratory examinations showed the following values (normal range): peripheral white cell count, 8900/μl (3500–8500); C-reactive protein, 2.19 mg/dl (<0.3); total bilirubin, 0.6 mg/dl (0.2–1.2); alkaline phosphatase, 1544 U/l (107–340); γ-glutamyl transpeptidase, 1030 U/l (11–64); asparate aminotransferase, 130 U/l (13–35); alanine aminotransferase, 140 U/l (5–35); amylase, 44 U/l (37–125). Hepatitis B surface antigen and antibody to hepatitis C virus were negative. Serum IgG, IgM, and IgE levels were 1960 mg/dl (870–1700), 77 mg/dl (33–190), and 370 (0–320), respectively. Antinuclear antibody was positive. Antimitochondrial antibody was negative. Among tumor markers, CEA, CA19-9, and soluble interleukin 2 receptor (sIL-2R) were 2.1 ng/ml (<5.0), 18.5 U/ml (<37), and 611 U/ml (<650), respectively. Abdominal computed tomography (CT) showed dilatation of common bile duct (Fig. 3a) and no significant pancreatic lesions (Fig. 3b). ERCP revealed irregular narrowing of the intrahepatic bile ducts (Fig. 3c) and no narrowing of the main pancreatic duct (Fig. 3d). Intraductal ultrasonography (IDUS) detected wall thickness of the intrahepatic and common bile ducts. Cytology of bile juice was negative for malignancy. She was diagnosed with PSC and treated with ursodeoxycholic acid.

Fig. 3
figure 3

Abdominal computed tomography (CT) images of case 2 on clinical onset. Abdominal CT showed a dilatation of common bile duct (a) and no significant pancreatic lesions (b), such as swelling of the pancreas. ERCP revealed irregular narrowing of the intrahepatic bile duct (c), and no narrowing of the main pancreatic duct (d)

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Four months after clinical onset, the patient was referred to our hospital for further evaluation of recurrent obstructive jaundice. Laboratory tests showed elevations of IgG4 to 206 mg/dl (4.8–105). Histopathological examination by liver biopsy showed moderate lymphoplasmacytic infiltration with fibrosis and fibrotic change surrounding the bile ducts in the enlarged portal area, which is compatible with PSC (Fig. 4a). However, an inflammation with abundant IgG4-positive plasma cells (16 cells/hpf) (Fig. 1d), a characteristic finding in IgG4-SC, was also found. Then, we suspected IgG4-SC, and steroid therapy was initiated at a dose of 30 mg/day. The dose of steroid was reduced by 5 mg/week until it reached 10 mg/day. MRCP revealed no improvements of the irregular narrowing of the intrahepatic lesion and the common bile duct after steroid therapy. One year later, her liver dysfunction developed into liver cirrhosis.

Fig. 4
figure 4

Histopathological findings of the liver (case 2). Histopathological examination by liver biopsy showed moderate lymphoplasmacytic infiltration with fibrosis and fibrotic change surrounding the bile ducts in the enlarged portal area (H&E staining ×100, a). IgG4-immunostaining of the liver specimens showed infiltration of abundant IgG4-positive plasma cells (×400, b)

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Case 3

The patient was a 23-year-old woman who was admitted to our hospital with the complaint of jaundice. ERCP revealed stricture of the lower common bile duct, irregular dilatation after confluent strictures, and many small defects in intrahepatic bile ducts (Fig. 5a). Endoscopic naso-biliary drainage (ENBD) was performed. The pancreatic-duct image showed no narrowing of the main pancreatic duct. Cytology of bile juice was negative for malignancy. Physical examination revealed no significant findings except for jaundice. Laboratory examinations showed the following values (normal range): peripheral white cell count, 10100/μl (3000–8500); peripheral eosinocyte count, 91/μl; C-reactive protein, 0.09 mg/dl (<0.3); total bilirubin, 5.0 mg/dl (0.2–1.2); alkaline phosphatase, 1750 U/l (107–323); γ-glutamyl transpeptidase, 211 U/l (8–45); asparate aminotransferase, 90 U/l (12–31); alanine aminotransferase, 101 U/l (6–24); amylase, 37 U/l (32–112). Hepatitis B surface antigen and antibody to hepatitis C virus were negative. Serum IgG, IgA, and IgM levels were 2570 mg/dl (1092–1577), 208 mg/dl (134–287), and 363 mg/dl (60–161), respectively. Rheumatoid factor, antinuclear antibody, and antimitochondrial antibody were negative. The irregular dilatation of bile ducts improved 5 months after a drainage procedure with a biliary plastic stent, but irregular narrowing of the intrahepatic bile ducts persisted (Fig. 5b). She was diagnosed with PSC and treated with ursodeoxycholic acid.

Fig. 5
figure 5

Endoscopic nasobiliary drainage (ENBD) cholangiogram and ERCP image of case 3 on clinical onset. Cholangiography through an ENBD tube revealed a stricture of the lower common bile duct, irregular dilatation after confluent strictures, and many small defects in intrahepatic bile ducts (a). ERCP after a drainage procedure with a biliary plastic stent revealed improvement of bile duct dilatation, but irregular narrowing of the intrahepatic bile ducts persisted (b)

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Three years after clinical onset, the patient was referred to our hospital for further evaluation of recurrent obstructive jaundice. Histopathological examination by liver biopsy showed an infiltration of lymphocytes and ductular proliferation in the portal area (Fig. 6a), and a few IgG4-positive plasma cells (1 cell/hpf) were detected (Fig. 6b). Laboratory tests showed elevations of IgG4 to 313 mg/dl (4.8–105). Therefore, we suspected IgG4-SC and steroid therapy was initiated at the dose of 30 mg/day. The dose of steroid was reduced by 5 mg/day biweekly until it reached 10 mg/day. MRCP revealed no improvements of strictures of the intrahepatic and the common bile ducts after steroid therapy.

Fig. 6
figure 6

Histopathological findings of the liver (case 3). Histopathological examination by liver biopsy showed moderate lymphoplasmacytic infiltration and ductular proliferation in the enlarged portal area (H&E staining ×200, a). IgG4-immunostaining of the liver specimens showed infiltration of few IgG4-positive plasma cells (×400, b)

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Discussion

Sarles et al. [13] observed the first case of pancreatitis with hypergammaglobulinemia, and Yoshida et al. first proposed the concept of autoimmune pancreatitis (AIP) in 1995 [14], in which patients show diffusely enlarged pancreas, narrowing pancreatogram, increased serum IgG, presence of autoantibodies, fibrotic changes with lymphocytic infiltration, and steroidal efficacy. Thereafter, many AIP cases have been reported by Japanese investigators, and AIP has been accepted as a new clinical entity [15–17]. Patients with AIP often show discomfort in the epigastrium, obstructive jaundice due to bile-duct stricture, and diabetes mellitus. AIP is more common in middle-aged and elderly men. Patients with AIP often also have extrapancreatic lesions such as biliary lesions, sialoadenitis, retroperitoneal fibrosis, enlarged celiac and hilar lymph nodes, chronic thyroiditis, and interstitial nephritis [18–23], which suggests that AIP may be a systemic disorder. In 2001, Hamano et al. [24] reported that patients with AIP have high serum IgG4 concentrations. Kamisawa et al. [1] proposed IgG4-related sclerosing disease. Recently, IgG4-SC was recognized as a disease entity characterized by sclerosing inflammation with an infiltration of abundant IgG4-positive plasma cells, and AIP was associated in most cases. Before establishing the concept of AIP, IgG4-SC used to be misdiagnosed as PSC complicating chronic pancreatitis. Therefore, differential diagnosis between IgG4-SC and PSC is important, because the effective treatments and the prognoses are different. Although IgG4-SC is usually associated with pancreatic lesions, a few patients with IgG4-SC have shown little pancreatic change or other organ involvement [25, 26]. The correct diagnosis of such cases is difficult.

In this study, we presented 3 PSC cases with elevated serum IgG4 levels and/or infiltration of abundant IgG4-positive plasma cells in the liver, which usually support the diagnosis of IgG4-SC. In the 3 cases presented, abdominal ultrasound and abdominal CT scan did not show inflammatory swelling of the whole pancreas, and ERCP did not show strictures over one-third of the main pancreatic duct (MPD), which is characteristic of AIP [27]. Cholangiography in these 3 patients showed strictures of the intrahepatic and common bile ducts, and no narrowing of the MPD. After steroid therapy, strictures of the intrahepatic and common bile ducts were not improved on MRCP images. These findings supported the diagnosis of PSC. In these 3 patients, however, there were findings atypical for PSC. First, the serum IgG4 concentrations in cases 2 and 3 were elevated. The Japanese criteria of AIP contain three approaches: pancreatic imaging, laboratory data, and histopathology [18]: (1) Pancreatic image examinations show the narrowing of the main pancreatic duct and enlargement of pancreas which are characteristic of the disease; (2) Laboratory data show the presence of autoantibodies, or elevated levels of serum gammaglobulin, IgG, or IgG4; (3) Histopathological examinations of the pancreas show fibrosis and pronounced infiltration of cells, mainly lymphocytes and plasmacytes. For a diagnosis, criterion (1) must be present, together with criterion (2) and/or (3). However, it is necessary to exclude malignant diseases such as pancreatic or biliary cancers. In the diagnostic criteria of Korea [28] and Asia [29], apparent pancreatic lesions comparable with AIP must be present for a diagnosis of AIP. Two patients (cases 2 and 3) did not fulfill the diagnostic Japanese, Korean, and Asian criteria, because they had no apparent pancreatic lesions comparable with AIP. Secondly, infiltration of abundant IgG4-positive plasma cells in the liver specimens was found in cases 1 and 2. IgG4 immunostaining showing >10 IgG4-positive plasma cells/hpf is suggestive of AIP in the HISORt criteria by the Mayo Clinic [30] and Korean criteria [28]. The presence of IgG4-SC in the HISORt criteria can be diagnosed in patients with effective steroid therapy. Two patients (cases 1 and 2) did not fulfill the HISORt criteria because they had no response to steroid therapy.

The role of IgG4 in patients with PSC has been used to differentiate clinical syndromes of atypical PSC cases. In 1991, Kawaguchi et al. [31] first described clinical and pathological features of variant cases of PSC, which were later known as sclerosing cholangitis complicated with autoimmune pancreatitis (AIP). In 1995, Takikawa et al. [32] analyzed 192 cases of Japanese PSC and found two peaks in the age distribution. Some cases in elderly patients were complicated with chronic pancreatitis, which was regarded as sclerosing cholangitis complicated with autoimmune pancreatitis. The patients in cases 1 and 3 were young, and case 2 was an elderly woman. In 2004, Takikawa et al. [33] analyzed 269 additional cases of Japanese PSC and showed that 7% of these cases had AIP. In a recent study, Mendes et al. [34] have reported that 12 (9%) of 127 PSC patients had elevated serum IgG4 levels. These patients also had significantly higher levels of ALP and total bilirubin, and higher PSC Mayo risk scores. Mendes’s study also reveals that IgG4-SC may have been included among PSC cases in the United States. There may possibly be disease entities such as overlap syndrome. In our cases, it is difficult to differentiate IgG4-SC from PSC on cholangiographic and immunohistochemical findings. The findings of elevated serum IgG4 levels and/or an infiltration of abundant IgG4-positive plasma cells in the liver usually support the diagnosis of IgG4-SC. On the other hand, the patients of cases 1 and 3 were younger, and the patient of case 1 was associated with UC. These clinical characteristics may be compatible with PSC. In a recent study, Kawabe et al. have reported an advanced state of biliary cirrhosis and atrophic pancreas but did not reveal typical imaging findings of AIP and AIP-related sclerosing cholangitis [35]. Hamano et al. have reported 3 patients with IgG4-SC who had no apparent pancreatic lesions comparable with AIP [26]. These cases were improved only by steroid therapy or drainage. In this study, however, our 3 patients with sclerosing cholangitis who had no apparent pancreatic lesions comparable with AIP did not respond to steroid therapy. Some AIP patients may develop pancreatic stones and the conventional type of chronic pancreatitis [36, 37]. Though there may be a possibility that far advanced stages of AIP with sclerosing cholangitis who had no pancreatic lesions might not respond to steroid therapy, the long-term untreated prognosis of AIP still remains unclear. Therefore, further studies are necessary. Finally, we diagnosed our 3 patients as PSC according to the commonly used diagnostic criteria for PSC [38]. They did not fulfill all criteria, and histopathological finding of the pancreas in case 1 did not show so-called LPSP. Here, our cases showed elevated serum IgG4 levels and/or an infiltration of abundant IgG4-positive plasma cells in patients with PSC, which do not respond to steroid therapy. Therefore, it is necessary to be aware of the possibility of PSC with these findings to correctly differentiate PSC from IgG4-SC. The mechanisms of increased serum IgG4 and the role of the infiltrated IgG4-positive plasma cells in the portal area still remain unclear at this time. Recent studies of immune tolerance and allergy show that high dose antigen exposures cause immune deviation both of Th2 response in favor of Th0/Th1, and in the generation of IL-10- and TGF-β-producing regulatory T cells [39], though our 3 patients were not found to have allergic disease. Additionally, IL-10 induces preferential switching of B cell response in favor of producing IgG4 antibodies, and possibly IgA antibodies under the influence of TGF-β [40]. Our previous data [41] and others [11] showed that IL-10 secreted from increased inducible peripheral regulatory T cells may be involved in switching B cells to produce IgG4-positive cells and increased serum IgG4 in IgG4-related sclerosing pancreatitis (autoimmune pancreatitis) or IgG4-related sclerosing cholangitis, but not in PSC [11]. These findings suggested that increased IgG4 may be reactive and involved in the pathophysiology of IgG4-related diseases, but not in the pathogenesis. Further studies are necessary to clarify the role of IgG4.

In conclusion, some of the patients with PSC show elevated serum IgG4 levels and/or an infiltration of abundant IgG4-positive plasma cells, and do not respond to steroid therapy.