Inside our bones is a soft, spongy tissue called bone marrow. It is the "factory" that makes your blood cells. This includes red cells that carry oxygen to your body, white cells that fight infection, and platelets that stop bleeding. Bone marrow failure happens when your bone marrow is unable keep up with your body's need for healthy blood cells. Aplastic anemia, acute myeloid leukemia (AML), myelodysplastic syndromes (MDS) and paroxysmal nocturnal hemoglobinuria (PNH) are bone marrow failure diseases.