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Secondary aplastic anemia is a failure of the bone marrow to make enough blood cells. All blood cell types are affected.

Secondary aplastic anemia is caused by injury to blood stem cells. Normal blood stem cells divide and turn into all blood cell types, mainly white blood cells, red blood cells, and platelets. When blood stem cells are injured, there is a reduction in all blood cell types.

This condition can be caused by:

• Certain drugs
• Chemotherapy
• Disorders present at birth (congenital disorders)
• Drug therapy to suppress the immune system
• Pregnancy
• Radiation therapy
• Toxins such as benzene or arsenic

When the cause is unknown, it is referred to as idiopathic aplastic anemia. In about half of all cases, no cause can be found.

The disease may be acute or chronic.

• Bleeding of the gums
• Bleeding of internal organs
• Easy bruising
• Fatigue
• Frequent or severe infections
• Nosebleeds
• Rapid heart rate
• Rash
• Shortness of breath during physical activity
• Weakness

Signs include:

• Low platelet count (thrombocytopenia)
• Low red blood cell count (anemia)
• Low white blood cell count (leukopenia)

Tests may include:

• Bone marrow biopsy
• Complete blood count (CBC)
• Reticulocyte count

In secondary aplastic anemia, removing the cause is critical. In some cases it can lead to recovery.

Mild cases of aplastic anemia may be treated with supportive care, or may not need treatment. Blood and platelet transfusions will help correct the abnormal blood counts and relieve some symptoms in moderate cases.

Severe aplastic anemia, which causes a very low blood-cell count, is a life-threatening condition. Younger patients with a severe case of the disease will need a bone marrow transplant. Older patients, or those who do not have a matched bone marrow donor, can be treated with medications that suppress the immune system, such as antithymocyte globulin (ATG), tacrolimus, or cyclosporine.

ATG consists of antibodies made in horses or rabbits against a type of white blood cell in humans called T cells. It is used to suppress the body's immune system, allowing the bone marrow to start generating blood cells again. Other medications to suppress the immune system, such as cyclosporine, tacrolimus, and cyclophosphamide (Cytoxan) also may be used. Corticosteroids and androgens have been used as well.

The condition usually gets worse unless the cause is removed or the disease is treated.

Untreated severe aplastic anemia usually gets worse, eventually leading to death. Mild and moderate forms of the disease can be slower.

Bone marrow transplant has been successful in young patients. It has a long-term survival rate of approximately 80%. Older patients have a survival rate of 40 - 70% after a transplant.

• Bleeding in the brain
• Death caused by bleeding, infectious complications of a bone marrow transplant, rejection of a bone marrow graft, or severe reactions to ATG
• Infection

Call your health care provider if:

• You have signs of infection, such as fever
• You bleed for no reason
• You are feeling extremely tired or short of breath with activity

Secondary aplastic anemia may be an unavoidable consequence of treatments such as chemotherapy. Avoid toxins such as benzene and arsenic, if possible.

Anemia - secondary aplastic; Acquired aplastic anemia

Castro-Malaspina H, O'Reilly RJ. Aplastic anemia and related disorders. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007: chap 171.

Updated by: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; and Yi-Bin Chen, MD, Leukemia/Bone Marrow Transplant Program, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.