A 50-year-old male who had frequent infections of his upper respiratory tract manifested with subcutaneous petechiae over his arms and legs. Investigations revealed low hemoglobin and a dry tap marrow. The most likely condition the patient is suffering from

Correct Answer: D

Rationale: The correct answer is D: Aplastic anemia. Aplastic anemia is characterized by pancytopenia, which includes low hemoglobin levels leading to anemia. The dry tap marrow indicates bone marrow failure, which is a hallmark of aplastic anemia. The subcutaneous petechiae are due to thrombocytopenia, another feature of this condition. Iron deficiency anemia (A) typically presents with microcytic hypochromic red blood cells and is not associated with bone marrow failure. Megaloblastic anemia (B) is characterized by macrocytic red blood cells and is usually due to deficiencies in vitamin B12 or folate. Hemolytic anemia (C) involves the premature destruction of red blood cells and is not typically associated with bone marrow failure.

Correct Answer: C

Rationale: The correct answer is C: Platelets change their shape during the process of platelet aggregation in vascular injury. Platelets undergo shape change from a discoid to a spiky form, leading to the exposure of their glycoprotein receptors, which then bind to fibrinogen and other platelets to form a platelet plug. This process is crucial for hemostasis and preventing excessive bleeding. Explanation for why other choices are incorrect: A: There will be initial vasodilation - Vasodilation is not a direct result of platelet aggregation but rather an initial response to vascular injury to increase blood flow to the area. B: Clotting factors play no role in its formation - Clotting factors are essential for the later stages of hemostasis, but platelet aggregation is primarily driven by platelet activation and shape change. D: Serotonin stimulates platelet aggregation - While serotonin is released from platelets upon activation, it does not directly stimulate platelet aggregation.

Correct Answer: B

Rationale: The correct answer is B because once a mosquito vector, usually Aedes aegypti, is infected with the dengue virus, it remains infective for life. This is due to the virus establishing a lifelong infection in the mosquito's salivary glands. A: Incorrect. Dengue is caused by an RNA virus, specifically the flavivirus. C: Incorrect. Aedes mosquitoes prefer clean, stagnant water for breeding, not polluted water. D: Incorrect. Joint symptoms are common in both dengue fever and chikungunya, but usually more severe in chikungunya.

Correct Answer: C

Rationale: Virchow's node, also known as the left supraclavicular node, receives lymphatics primarily from the abdomen. The correct answer is C (prostate) because the prostate does not drain into Virchow's node. The stomach, breast, and testes all have lymphatic connections to Virchow's node. This is due to the anatomical location of these organs and their respective lymphatic drainage pathways. The stomach drains into the celiac lymph nodes, which then connect to Virchow's node. The breast drains into the axillary lymph nodes, which also communicate with Virchow's node. The testes drain into the para-aortic lymph nodes, which eventually lead to Virchow's node. Therefore, C is the correct answer based on the unique lymphatic drainage patterns of these organs.

Correct Answer: D

Rationale: In thrombasthenia, there is a deficiency or dysfunction of integrin αIIbβ3 (GPIIb/IIIa), leading to impaired platelet aggregation. Prolonged bleeding time (A) is seen due to defective platelet function. Platelet count (B) is typically normal as thrombasthenia does not affect platelet production. Platelet aggregation defect (C) is a characteristic feature of thrombasthenia. Prolonged clotting time (D) is not associated with thrombasthenia as it primarily affects platelet function, not the coagulation cascade. Hence, choice D is the correct answer.