Road to a Cure Pedal for PSC

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PSC and PBC

PSC and PBC


Table 1: Similarities and differences between PSC and PBC

Feature
PSC – primary sclerosing cholangitis
PBC – primary biliary cholangitis (commonly still referred to as primary biliary cirrhosis)
 Site of disease involvement  Bile ducts inside and outside the liver; however in small duct PSC (10-15% of patients) only the small ducts inside the liver are affected  Small bile ducts inside the liver only
Mode of diagnosis Usually by MRI of bile ducts. Occasionally liver biopsy or ERCP is needed Two of the following: Raised ALP, positive disease specific antibodies (AMA), diagnostic liver biopsy.
Associated with increased risk of bile duct cancer and colon cancer Yes No
Response to ursodeoxycholic acid (UDCA) Improves liver blood tests in some patients; not conclusively proven to slow disease progression Associated with improved prognosis in those individuals who respond well to UDCA
Co-existing inflammatory bowel disease (IBD) Around 80% of patients have IBD – mostly colitis  Very rare and not characteristic; around 1%
Common symptoms in early disease Itching, fatigue, abdominal pain, cholangitis flares Itching, fatigue, dry eyes and mouth, abdominal pain
Gender predominance 60% men, 40% women 90% women, 10% men
Average age at diagnosis Any age; mostly around 40 years 75% are affected in middle age (>45 years old)
Associated with excess alcohol consumption No No
Associated with smoking history Most often non-smokers Associated with a history of smoking

In PSC, a key feature is the development of scar tissue (fibrosis) that predominantly affects the medium- to large-sized bile ducts within and outside the liver. This can most often be identified with a special MRI scan (called MRCP), although occasionally a liver biopsy is needed for confirmation. PSC can affect men and women at any age, although it is commonly diagnosed in the fourth decade of life, most often in the presence of inflammatory bowel disease (IBD) [2].

Close monitoring of PSC patients is vital. Because of the increased colon cancer risk in PSC patients with ulcerative colitis, annual colonoscopies are advised.  Moreover, the presence of colitis is associated with a greater risk of liver disease progression and bile duct cancer (cholangiocarcinoma) [4]. Individuals with PSC can occasionally develop abdominal pain and fever, which may suggest infection of the bile ducts called cholangitis. Although the latter can be treated with antibiotics, no currently known treatment has been shown to slow the progression or cure PSC. There are, however, several clinical trials underway that aim to slow progression of liver disease [5].

By contrast, PBC mainly affects the small bile ducts in the liver itself and is not associated with biliary sclerosis [6]. In the current era, PBC can be identified through special antibody tests (performed on blood sampling) and liver biopsy is rarely needed. Over 90% of individuals with PBC are women, and the condition is most often diagnosed in middle age via a series of blood tests (seeTable 1). Approximately two-thirds of patients with PBC can improve their liver blood tests whilst taking ursodeoxycholic acid (UDCA), and it is well recognized that this correlates with improved survival and a lower risk of liver transplantation [3]. Unlike primary sclerosing cholangitis, PBC does not share an association with IBD, colonic cancer or bile duct cancer; however individuals with PBC can occasionally develop thyroid problems, dry eyes (a condition called ‘Sicca syndrome/Sjogren’ssyndrome) or intolerance to gluten in wheat (coeliac disease) [7].

It is important to recognize that PBC and PSC are different diseases; stemming from the way they are diagnosed, the association with IBD, and the way they are monitored and respond to treatment. The layers of complexity in PSC require the care of clinicians experienced in treating PSC and knowledgeable in current PSC research.