A 50-year-old man presents with progressive jaundice, dark urine, and pruritus. Imaging reveals a mass in the head of the pancreas. What is the most likely diagnosis?

Correct Answer: A

Rationale: The most likely diagnosis for a 50-year-old man with jaundice, dark urine, pruritus, and a mass in the head of the pancreas is pancreatic cancer. Pancreatic cancer commonly presents with obstructive jaundice due to compression of the common bile duct by the tumor in the head of the pancreas. This leads to dark urine (due to increased bilirubin) and pruritus. Chronic pancreatitis typically presents with recurrent abdominal pain, not progressive jaundice. Gallstones can cause obstructive jaundice but are not associated with a mass in the pancreas. Primary sclerosing cholangitis presents with jaundice, but it typically involves intrahepatic and extrahepatic bile ducts, not the pancreas.

Correct Answer: A

Rationale: The most likely diagnosis is Primary biliary cirrhosis (PBC). PBC typically presents with jaundice, pruritus, and dark urine due to impaired bile flow. Elevated bilirubin and alkaline phosphatase levels are common in PBC. Imaging findings of dilated intrahepatic bile ducts and a normal common bile duct support the diagnosis of PBC. Primary sclerosing cholangitis (Choice B) would show strictures and beading of bile ducts on imaging. Gallstones (Choice C) would typically present with a common bile duct obstruction. Pancreatic cancer (Choice D) may present with similar symptoms but is less likely given the specific imaging findings in this case.

Correct Answer: C

Rationale: The most likely diagnosis is primary sclerosing cholangitis (PSC) based on the patient's symptoms of fatigue, pruritus, jaundice, and elevated bilirubin and alkaline phosphatase levels. PSC is commonly associated with inflammatory bowel disease, such as ulcerative colitis. The characteristic findings of elevated alkaline phosphatase and bilirubin levels are indicative of cholestasis, which is a key feature of PSC. Additionally, PSC is characterized by fibrosis and inflammation of the bile ducts, leading to bile duct strictures and subsequent liver damage. Hepatitis B would present with viral hepatitis symptoms and different lab findings. Primary biliary cirrhosis typically presents with elevated alkaline phosphatase and antimitochondrial antibodies. Autoimmune hepatitis would have elevated transaminases and autoantibodies. Therefore, based on the clinical presentation and lab results, PSC is the most likely diagnosis.

Correct Answer: B

Rationale: The correct answer is B: Celiac disease. The patient's symptoms of abdominal pain, bloating, diarrhea, and improvement with fasting are classic for celiac disease, an autoimmune condition triggered by gluten ingestion. Her iron deficiency anemia can be attributed to malabsorption common in celiac disease. Irritable bowel syndrome (A) typically presents with abdominal pain relieved by defecation, not fasting. Lactose intolerance (C) results in symptoms after consuming dairy, not necessarily improved by fasting. Crohn's disease (D) may present similarly, but the improvement with fasting and iron deficiency anemia point more towards celiac disease in this case.

Correct Answer: B

Rationale: The correct answer is B: Hemochromatosis. In this case, the patient's symptoms of fatigue, arthralgia, darkening of the skin, elevated liver enzymes, and high serum ferritin levels point towards iron overload disorder. Hemochromatosis is a genetic condition characterized by excessive absorption and accumulation of iron in various organs, leading to liver damage and skin pigmentation. Wilson's disease (A) presents with copper accumulation, not iron. Alpha-1 antitrypsin deficiency (C) primarily affects the lungs and liver, not causing iron overload. Autoimmune hepatitis (D) does not typically present with elevated ferritin levels.