A 55-year-old man with constipation, Hb 10 g/dL, MCV 72 fL, low serum iron, high iron-binding capacity, and low ferritin. Best next step in evaluation?

Correct Answer: C

Rationale: The correct answer is C: Colonoscopy. This is the best next step in evaluation for this patient because the presentation suggests iron deficiency anemia. The low serum iron, high iron-binding capacity, and low ferritin levels are consistent with this diagnosis. Colonoscopy is indicated to rule out gastrointestinal bleeding as the cause of iron deficiency anemia in a middle-aged man with no other obvious etiology. Red blood cell folate (choice A) and serum lead levels (choice B) are not indicated based on the clinical presentation. Bone marrow examination (choice D) is not needed at this point as the likely cause of anemia is iron deficiency related to possible gastrointestinal bleeding.

Correct Answer: C

Rationale: The correct answer is C: APC. This gene mutation is associated with familial adenomatous polyposis (FAP), a condition characterized by hundreds to thousands of colorectal polyps and a high risk of developing colon cancer. FAP is an autosomal dominant disorder, so individuals with a family history of colon cancer are at highest risk for having an APC mutation. MEN1 (choice A) is associated with multiple endocrine neoplasia type 1, RET (choice B) with multiple endocrine neoplasia type 2, and MSH (choice D) with Lynch syndrome - all of which are not specifically linked to colon cancer in the context of this question.

Correct Answer: C

Rationale: The most important initial step in a 30-year-old woman on propylthiouracil with fever and sore throat is to perform a CBC. This is crucial to assess for potential agranulocytosis, a rare but serious side effect of propylthiouracil leading to severe neutropenia. A CBC will reveal any abnormalities in white blood cell counts, particularly neutrophils, guiding immediate management. Checking serum TSH or T3 levels is not necessary in this acute situation and won't provide immediate actionable information. A chest x-ray is not indicated unless there are specific respiratory symptoms or clinical signs suggesting a need for imaging.

Correct Answer: A

Rationale: The correct answer is A: Hypercalcemia. In lung cancer, paraneoplastic syndromes can occur due to tumor-secreted substances affecting distant organs. Hypercalcemia is commonly associated with lung cancer and can cause confusion. SIADH (B) is more common in small cell lung cancer. Hypoglycemia (C) is not a typical paraneoplastic syndrome in lung cancer. Migratory thrombophlebitis (D) is associated with pancreatic cancer, not lung cancer.

Correct Answer: C

Rationale: The correct answer is C because taking aspirin can worsen thrombocytopenia by further reducing platelet function, leading to increased risk of bleeding. Aspirin is a known blood thinner and can exacerbate the condition in a patient with low platelet count. Choices A, B, and D are not as concerning because bruising easily, soft dark bowel movements, and decreased appetite can be common side effects of chemotherapy and not directly related to worsening thrombocytopenia.