Aplastic anaemia. Light micrograph of a bone marrow smear showing red blood cell (erythrocyte) aplasia. Aplasia is a total or partial failure in cell production. On this frame there are much fewer red blood cells (small grey) than would be expected in normal marrow. The larger cells (blue) are white blood cells. Failure of the bone marrow in red blood cell aplasia can be triggered by cancer treatment, viruses or toxins. Fewer red blood cells going into the bloodstream results in aplastic anaemia characterized by fatigue, breathlessness and bleeding nose and gums. Without a bone marrow transplant severe aplastic anaemia is often fatal. Magnification unknown.