A 40-year-old man presents with abdominal pain, diarrhea, and weight loss. He has a history of Crohn's disease. Laboratory tests reveal low hemoglobin and elevated ESR. What is the most likely diagnosis?

Correct Answer: D

Rationale: The correct answer is D: Crohn's disease flare. Given the patient's history of Crohn's disease, symptoms of abdominal pain, diarrhea, weight loss, and abnormal lab findings (low hemoglobin, elevated ESR) are indicative of a flare-up of Crohn's disease. This is supported by the clinical presentation and the lab results. Ulcerative colitis (A) presents differently with rectal bleeding and mucous diarrhea. Irritable bowel syndrome (B) does not typically cause weight loss or abnormal lab findings. Celiac disease (C) would present with malabsorption symptoms and specific antibodies, not consistent with this patient's presentation. Crohn's disease flare (D) is the most likely diagnosis based on the information provided.

Correct Answer: B

Rationale: The most likely diagnosis is Celiac disease (Choice B) due to the patient's symptoms of abdominal pain, bloating, diarrhea, and improvement with fasting, which are consistent with malabsorption seen in Celiac disease. The history of iron deficiency anemia also supports this, as it is a common complication of Celiac disease due to impaired absorption of nutrients. Irritable bowel syndrome (Choice A) typically does not improve with fasting, lactose intolerance (Choice C) does not usually cause iron deficiency anemia, and Crohn's disease (Choice D) typically presents with more severe symptoms and different patterns of improvement.

Correct Answer: A

Rationale: The most likely diagnosis for a 60-year-old man with fatigue, polyuria, polydipsia, hyperglycemia, and ketonuria is Type 1 diabetes mellitus. The key clues are the presence of ketonuria, which indicates the body is breaking down fats for energy due to lack of insulin in Type 1 diabetes. Additionally, the acute onset of symptoms in an older individual suggests an autoimmune destruction of pancreatic beta cells seen in Type 1 diabetes. Type 2 diabetes is less likely due to the acute presentation and ketonuria. Diabetes insipidus presents with polyuria but not hyperglycemia or ketonuria. Hyperthyroidism typically presents with symptoms such as weight loss, tremors, and heat intolerance, not the classic symptoms seen in this case.

Correct Answer: A

Rationale: The most likely diagnosis is A: Primary biliary cirrhosis. This is supported by the patient's symptoms of fatigue, pruritus, jaundice, elevated bilirubin and alkaline phosphatase levels, and dilated intrahepatic bile ducts. Primary biliary cirrhosis is an autoimmune liver disease that primarily affects middle-aged women, leading to destruction of intrahejson hepatic bile ducts. The normal common bile duct rules out obstruction from gallstones or pancreatic cancer. Primary sclerosing cholangitis typically presents with strictures in the bile ducts, which is not seen in this case. Therefore, the combination of symptoms, lab findings, and imaging results point towards primary biliary cirrhosis as the most likely diagnosis.

Correct Answer: A

Rationale: The correct answer is A: Hypothyroidism. In this scenario, the patient has symptoms of hypothyroidism (fatigue, weight gain, cold intolerance) along with high TSH and low free T4 levels, indicating primary hypothyroidism. TSH is elevated as the body is trying to stimulate the thyroid to produce more thyroid hormones. Free T4 is low as the thyroid is not able to produce enough hormones. Hyperthyroidism (choice B) would present with low TSH and high free T4 levels. Thyroiditis (choice C) typically presents with symptoms of hyperthyroidism followed by hypothyroidism. Thyroid cancer (choice D) usually does not cause these specific symptoms and lab findings. Therefore, based on the symptoms and lab results, hypothyroidism is the most likely diagnosis.