Aplastic Anemia

– A reduction in the number of circulating red blood cells resulting from bone marrow failure and generally accompanied by agranulocytosis and/or thrombocytopenia.

Causes and Incidence

The etiology is unknown in half of diagnosed cases; the other half are induced by chemicals, drugs, viruses, or radiation. The incidence is low.

Disease Process

Exposure to a known or unknown toxin depresses production of erythrocytes, platelets, and granulocytes in the bone marrow. Common toxins include ionizing radiation, chemical agents (e.g., benzene, DDT, carbon tetrachloride), and drugs (e.g., antitumor or antimicrobial agents).


The onset is usually insidious, occurring weeks or months after exposure to the toxin. Fatigue, weakness, dyspnea, and waxy pallor of the skin and mucous membranes are characteristic. Thrombocytopenia causes hemorrhage into mucous membranes, skin, and optic fundi. Agranulocytosis leads to severe infection.

Potential Complications

Chronic anemia leads to increasing hemorrhage and repeated infections, which result in death in about half of those diagnosed.

Diagnostic Tests

Complete blood count (CBC)
Decreased RBCs (normochromic, normocytic), WBCs, and hemoglobin (Hgb).

Platelet count

Serum iron

Bone marrow biopsy
Hypocellular/hypoplastic; fatty, fibrous tissue.

Reticulocyte count
Markedly decreased.


Surgery – None.

Drugs – Corticosteroids to stimulate granulocyte production; antibiotics for infection; androgens to stimulate bone marrow.

Removal of causative agent; bone marrow transplant from a human leukocyte antigen (HLA)-matched donor (sibling); blood transfusions; hemorrhage precautions.