50-year-old with infections, petechiae, dry marrow tap. Condition?

Correct Answer: D

Rationale: The correct answer is D: Aplastic anemia. In a 50-year-old with infections, petechiae, and a dry marrow tap, the presentation is indicative of bone marrow failure, characteristic of aplastic anemia. This condition results in pancytopenia, leading to infections, bleeding (petechiae), and a dry tap on bone marrow aspiration. Iron deficiency anemia (A) typically presents with microcytic hypochromic red blood cells, megaloblastic anemia (B) with macrocytic red blood cells, and hemolytic anemia (C) with evidence of red blood cell destruction.

Correct Answer: C

Rationale: The correct answer is C because a hapten is a small chemical grouping that can bind to preformed antibodies but cannot induce an immune response on its own. Haptens require a carrier molecule to become immunogenic. Choice A (An epitope) is incorrect because an epitope is the specific part of an antigen recognized by an antibody. Choice B (A paratope) is incorrect as a paratope is the part of an antibody that binds to an antigen. Choice D (A carrier) is incorrect because a carrier is a molecule that can bind to a hapten to make it immunogenic.

Correct Answer: A

Rationale: Step 1: Basophils are a type of leukocyte, so they are included in the total leukocyte count. Step 2: Basophils make up less than 0.2% of total leukocytes in the blood. Step 3: Therefore, choice A is correct as basophils comprise a very small percentage of leukocytes. Summary: Choice B is incorrect as basophil granules stain with basic dyes like Toluidine blue. Choice C is incorrect as basophils have a shorter lifespan compared to several months. Choice D is incorrect as basophils play a key role in anaphylaxis through the release of histamine.

Correct Answer: B

Rationale: The correct answer is B because the spleen does not store extra iron in ferritin. The spleen functions primarily to destroy old or defective red blood cells (choice A), break down hemoglobin (choice C), and store platelets not circulating (choice D). The spleen does not have a significant role in iron storage; that function is mainly carried out by the liver and bone marrow. Therefore, choice B is incorrect.

Correct Answer: A

Rationale: The correct answer is A: Male-to-male sexual contact. This is because statistics show that men who have sex with men (MSM) are the group most affected by new cases of HIV. MSM is considered a high-risk group due to various factors like higher prevalence of HIV within the community, higher rates of unprotected sex, and multiple sexual partners. Choice B is incorrect as heterosexual contact has a lower incidence rate compared to MSM. Choice C is incorrect as the combination of male-to-male sexual contact with injection drug use is less common than MSM alone. Choice D is incorrect because age group 25 to 29 may not necessarily be the most affected group in terms of new HIV cases.