Aplastic anemia (AA) is a disease in which the bone marrow, and the blood stem cells that reside there, are damaged. This causes a deficiency of all three blood cell types (pancytopenia): red blood cells (anemia), white blood cells (leukopenia), and platelets (thrombocytopenia).
Pancytopenia is a condition in which there is deficiency of RBCs, WBCs, and Platelets in blood. Aplastic anemia is one of the diseases that is a major cause of the condition called pancytopenia. There are other causes of pancytopenia such as myelofibrosis, metastatic solid tumors, myelodysplastic syndrome etc.