Myelodysplastic syndromes are a group of clonal stem cell disorders. Which of the following type has the poorest prognosis according to the FAB system of classifications?

Correct Answer: D

Rationale: The correct answer is D: RA with excess blasts in transformation. This choice has the poorest prognosis because it represents a progression of RA with excess blasts, indicating a higher percentage of blast cells in the bone marrow. This progression signifies a more aggressive form of the disease with a worse outcome. A: Refractory anemia (RA) is a milder form with a better prognosis compared to the other choices. B: RA with ring sideroblasts is a subtype of RA, and while it may have some adverse features, it generally has a better prognosis than RA with excess blasts. C: RA with excess blasts represents a higher risk group, but it is not as severe as RA with excess blasts in transformation, which indicates a further deterioration of the disease. In summary, D is the correct answer because it signifies the most advanced stage of the disease with the highest risk and poorest prognosis compared to the other choices.

Correct Answer: A

Rationale: Step 1: Visceral leishmaniasis is transmitted by sand flies. Step 2: In the Asian region, the main vector of visceral leishmaniasis is Phlebotomus species. Step 3: Phlebotomus species are known to transmit the Leishmania parasite in Asia. Step 4: Lutzomyia species are the main vector in the Americas. Step 5: Anopheles species are vectors for malaria, not leishmaniasis. Step 6: Mansonia species are vectors for diseases like filariasis, not leishmaniasis. Summary: Choice A is correct because Phlebotomus species are the main vector of visceral leishmaniasis in the Asian region, while choices B, C, and D are incorrect as they are not the main vectors for this disease in that specific geographical area.

Correct Answer: A

Rationale: The correct answer is A: vasculitis. Thalassemia major primarily causes abdominal pain due to complications such as splenic infarction, dragging pain from splenomegaly, and pigment stones in the gall bladder. Vasculitis is not a common complication of thalassemia major, making it the exception. Vasculitis is inflammation of blood vessels, not typically associated with abdominal pain in thalassemia. Therefore, A is the correct answer.

Correct Answer: A

Rationale: The correct answer is A because gum bleeding is not a characteristic of chronic phenytoin therapy. Phenytoin is used to treat seizures and does not directly cause gum bleeding. Aplastic anemia (B), scurvy (C), and hemophilia (D) are conditions that can lead to gum bleeding. Aplastic anemia is a bone marrow disorder, scurvy is a vitamin C deficiency, and hemophilia is a blood clotting disorder. Therefore, they are associated with gum bleeding.

Correct Answer: B

Rationale: The correct answer is B: hydroxyurea. Sideroblastic anemia is characterized by defective heme synthesis, leading to iron accumulation in mitochondria. Pyridoxine (A) can help in some cases by improving heme synthesis. Desferroxamine (C) is an iron-chelating agent used to remove excess iron. Androgens (D) can stimulate erythropoiesis. Hydroxyurea (B) is not used to treat sideroblastic anemia but is commonly used in conditions like sickle cell disease to increase fetal hemoglobin levels. Therefore, it is the correct choice.