Anemia, Aplastic

Incidence in USA: 2000 new cases/y.

• Per million up to age 9.

Southeast Asia and South Africa have 10-20 times higher incidence.

Within USA, related to agricultural areas or petrochemical industry and chemical exposures.

Infection

Hemorrhage

LV dysfunction due to high-output state and fluid overload

Sepsis

Coexisting congenital anomalies, especially renal and cardiac

Concomitant GI and intracranial hemorrhage

Difficulty cross-matching blood products after previous multiple transfusions

Self-perpetuating disorder resulting in pancytopenia due to a congenital or acquired loss of hemopoietic pluripotent stem cells.

Fanconi anemia is congenital familial marrow hypoplasia associated with intellectual disability and kidney, spleen, and skeletal hypoplasia.

Estren-Dameshek anemia is inherited marrow hypoplasia without physical abnormalities.

Pathophysiology: Reduction or dysfunction of pluripotent stem cells or their microenvironment from toxic or immunologic causes.

Prognosis for long-term survival has increased to 40% to 75% in those treated with antilymphocyte serum and 60% to 80% in those treated with BMT.

Two forms of drug-induced aplastic anemia are possible:

• Hypersensitivity: Not related to dose or duration.

• “Reversible” reaction: Often resolves with discontinuation; severity proportional to dosage.

Of cases, 50% to 75% are idiopathic.

Fanconi anemia demonstrates autosomal recessive inheritance with heterozygote frequency of 1 in 300,000-600,000 in USA.

Drug-induced: Chloramphenicol, NSAIDs, antiepileptics, and gold and sulfa group-containing compounds.

Environmental toxins include aromatic hydrocarbons (benzene, naphthalene, toluene, and glue), pesticides (DDT and lindane), and radiation.

Infectious causes include hepatitis C, CMV, EBV, HIV, TB, and toxoplasmosis.

Sequelae of other processes such as pancreatitis, pregnancy, lupus erythematosus, paroxysmal nocturnal hemoglobinemia, thymoma, and thymic CA.