PSC (Primary Sclerosing Cholangitis) – Top USMLE Diseases

Primary sclerosing cholangitis (PSC) is an inflammatory disease that causes fibrosis and strictures of the intrahepatic and extrahepatic bile ducts. The exact etiology is unknown, but there is a strong association with inflammatory bowel disease (IBD). Patients typically present with an insidious onset of fatigue, pruritus, and jaundice, which can progress to cirrhosis and complications related to biliary obstruction. The diagnosis is established with magnetic resonance cholangiopancreatography (MRCP) or endoscopic retrograde cholangiopancreatography (ERCP). Liver transplantation is the only definitive treatment and is indicated in patients with advanced liver disease.

The hepatobiliary system is composed of the liver, gallbladder, and bile ducts (within the liver and external to the liver). The liver produces bile, which is a fluid made of cholesterol, phospholipids, conjugated bilirubin, bile salts, electrolytes, and water. Bile, which assists in digestion and helps eliminate waste products, is stored in the gallbladder. The hepatobiliary system can be affected by infections, cysts, solid masses, ischemia, and mechanical flow obstruction, which mandate the presence of reliable imaging tests to determine the etiology. The methods that evaluate structural changes in the liver and biliary tract include ultrasonography, CT scan, and MRI (including magnetic resonance cholangiopancreatography). Additionally, cholescintigraphy, a functional imaging study, helps identify gallbladder pathology by tracking the biliary pathway.

Liver function tests, also known as hepatic function panels, are one of the most commonly performed screening blood tests. Such tests are also used to detect, evaluate, and monitor acute and chronic liver diseases. Liver function tests assess the levels of various hepatic proteins and enzymes to determine the state of liver metabolic activity, homeostasis, bile metabolism, and protein synthesis capacity. The standard hepatic panel includes the levels of total protein, bilirubin, albumin, ALT, AST, AST/ALT ratio, and alkaline phosphatase (ALP).

Immunosuppressants are a class of drugs widely used in the management of autoimmune conditions and organ transplant rejection. The general effect is dampening of the immune response. There are multiple targets in the immune system, as well as varied mechanisms in inhibiting inappropriate immune activity. Biologic agents are medications derived from living organisms that target particular components of the immune system. The targets can be tumor necrosis factor (TNF), interleukins (ILs), or B- or T-cell activity. Calcineurin inhibitors halt the activity of calcineurin, a phosphatase involved in T-cell activation. Corticosteroids interfere with the cell cycle of inflammatory cells and modify the activity of other immune components. mTOR inhibitors are proliferation signal inhibitors, reducing immune-cell proliferation. Some immunosuppressants, such as cytotoxic agents, have antineoplastic activity; these are used in rheumatoid arthritis, as prophylaxis for transplant rejection, and for malignant diseases.

Primary sclerosing cholangitis (PSC) is an inflammatory disease that causes fibrosis and strictures of the bile ducts. The exact etiology is unknown, but there is a strong association with inflammatory bowel disease (IBD). Patients typically present with an insidious onset of fatigue, pruritus, and jaundice, which can progress to cirrhosis and complications related to biliary obstruction. The diagnosis is established with magnetic resonance cholangiopancreatography (MRCP) or endoscopic retrograde cholangiopancreatography (ERCP). Liver transplantation is the only definitive treatment and is indicated in patients with advanced liver disease.

Autoimmune hepatitis (AIH) is a rare form of chronic liver disease in which the immune system attacks the liver causing inflammation. It predominantly affects women. Clinical presentation ranges from asymptomatic cases to patients that present with symptoms of acute liver failure (jaundice, right upper quadrant pain). Because AIH has a 40% mortality in 6 months without treatment, early diagnosis and treatment are imperative. Diagnosis is established by detecting anti-smooth muscle antibodies and performing a confirmatory liver biopsy. Treatment includes corticosteroids and azathioprine. If treatment is initiated early in the disease course, the prognosis is favorable.