Dengue is a common vector-borne disease prevalent in tropical countries. Which of the following statement is true for dengue fever?

Correct Answer: B

Rationale: The correct answer is B because the Aedes mosquito, the vector for dengue fever, remains infective for life once it is infected with the dengue virus. This is due to the virus establishing a lifelong infection in the mosquito's salivary glands. The other choices are incorrect because: A) Dengue is caused by an RNA virus, not a DNA virus. C) The Aedes mosquito prefers clean, stagnant water for breeding, not polluted water. D) Joint symptoms are commoner in chikungunya, not dengue fever.

Correct Answer: D

Rationale: In thrombasthenia, there is a deficiency or dysfunction of the glycoprotein IIb/IIIa receptor complex on platelets, leading to impaired platelet aggregation. This results in prolonged bleeding time due to ineffective platelet plug formation (choice A). Platelet count is typically normal (choice B). Platelet aggregation is defective (choice C). However, clotting time is not affected in thrombasthenia as it primarily involves platelet function, not the clotting factors involved in coagulation (choice D). Therefore, the correct answer is D.

Correct Answer: A

Rationale: Henoch-Schonlein purpura (HSP) is a vasculitis that primarily affects small blood vessels. Thrombocytopenia, which is a low platelet count, is not typically associated with HSP. Palpable purpura, intestinal intussusception, and acute diffuse glomerulonephritis are commonly seen in HSP due to immune-mediated inflammation of blood vessels, gastrointestinal involvement, and renal complications. Thrombocytopenia, on the other hand, is not a characteristic feature of HSP, making choice A the correct answer.

Correct Answer: A

Rationale: The correct answer is A, hyperchlorhydria. Pernicious anemia is characterized by vitamin B12 deficiency due to lack of intrinsic factor. Hyperchlorhydria refers to high stomach acid production, not a symptom of pernicious anemia. Premature graying of hair and gastric polyp are potential features of pernicious anemia. Anti intrinsic factor antibody presence in 60% of patients is a characteristic finding in pernicious anemia.

Correct Answer: D

Rationale: The correct answer is D: immunogenic thrombocytopenia. Platelet transfusion is not indicated in immunogenic thrombocytopenia because it involves antibodies attacking platelets, which would render transfused platelets ineffective. Platelet transfusion is indicated in aplastic anemia (A) to increase platelet count, in uremia with bleeding (B) to replace dysfunctional platelets, and in DIC (C) to help manage severe bleeding. In summary, platelet transfusion is contraindicated in immunogenic thrombocytopenia due to ineffective platelet response.