This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
Pancytopenia with a cellular marrow is seen in all except - 
Select and explain. 
A. PNH, B. Megaloblastic anemia, C. Myelodysplastic syndrome, D. Congenital dyserythropoietic anemia
D: Congenital dyserythropoietic anemia
Answer: D: Congenital dyserythropoietic anemia 
Explanation: None