Pancytopenia with hypercellular bone marrow is seen in which of the following conditions?

Both (Paroxysmal nocturnal hemoglobinuria) PNH and Megaloblastic anemia can present with hypercellular bone marrow. The bone marrow in megaloblastic anemia is usually hypercellular but it can be normal, hypercellular or hypocellular in PNH. So, megaloblastic anemia is the best answer of choice. Ref: Harrison's Principles of Internal Medicine 11th Edition, Page 616; 17th Edition, Page 661, 663; Haematology by Hoffman, Benz, Shattil et al 9lh Edition, Page 393; Robbin's Basic pathology, 7th Edition, Page 638; Hematology: Basic Principles and Practice, 4th Edition, Page 393.