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

Cellular marrow may refer to normocellular, hypocellular or hypercellular bone marrow. Both Paroxysmal nocturnal hemoglobinuria and Megaloblastic anemia are associated with cellular bone marrow. Megaloblastic anemia is associated with hypercellular bone marrow. PNH can have a normo, hypo or hypercellular bone marrow and is a primary bone marrow disease, making it the best answer of choice. Ref: Harrison 16th Edition, Page 617, 17th Edition, Page 663, table 102-1; Harrison's Principles of Internal Medicine, 17th Edition, Page 693; Davidson's Principles and Practice of Medicine, 20th Edition, Chapter 24, Page 1046.