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Key Features

Essentials of Diagnosis

  • Pancytopenia

  • No abnormal hematopoietic cells seen in blood or bone marrow

  • Hypocellular bone marrow

General Considerations

  • In aplastic anemia, bone marrow failure arises from suppression of or injury to the hematopoietic stem cell

  • Bone marrow becomes hypoplastic, fails to produce mature blood cells, and pancytopenia develops

Causes of aplastic anemia

  • "Idiopathic" (probably autoimmune)

  • In some cases of "idiopathic" aplastic anemia, defects in maintenance of the hematopoietic stem cell telomere length (dyskeratosis congenita) or in DNA repair pathways (ie, Fanconi anemia) have been identified

    • Likely linked to initiation of marrow failure

    • May be associated with progression to myelodysplasia, paroxysmal nocturnal hemoglobinuria (PNH), or acute myeloid leukemia

  • Complex detrimental immune response to viruses

  • Drugs

    • Chloramphenicol

    • Phenylbutazone

    • Gold salts

    • Sulfonamides

    • Phenytoin

    • Carbamazepine

    • Quinacrine

    • Tolbutamide

  • Chemotherapy, radiotherapy

  • Systemic lupus erythematosus

  • Toxins: benzene, toluene, insecticides

  • Posthepatitis

  • Pregnancy

  • Paroxysmal nocturnal hemoglobinuria

  • Congenital (rare)

Clinical Findings

Symptoms and Signs

  • Weakness and fatigue from anemia

  • Vulnerability to bacterial or fungal infections from neutropenia

  • Mucosal and skin bleeding from thrombocytopenia

  • Pallor, purpura, and petechiae

  • Hepatosplenomegaly, lymphadenopathy, or bone tenderness should not be present

Differential Diagnosis

  • Acute leukemia

  • Hairy cell leukemia

  • Hypocellular forms of myelodysplasia

  • Bone marrow infiltrative process (eg, tumor, infection, granulomatous disease)

  • Hypersplenism

  • Systemic lupus erythematosus

  • Nutritional deficiency (eg, vitamin B12 or folate)

  • Immune thrombocytopenia

Diagnosis

Laboratory Tests

  • Pancytopenia, although in early disease only one or two cell lines may be reduced

  • Anemia may be severe

  • Reticulocytopenia always present

  • Red blood cell morphology unremarkable, but there may be mild macrocytosis (increased MCV)

  • Neutrophils and platelets reduced in number, no immature or abnormal forms seen

  • Severe aplastic anemia defined by neutrophils < 500/mcL, platelets < 20,000/mcL, reticulocytes < 1%, and bone marrow cellularity < 20%

Diagnostic Procedures

  • Bone marrow aspirate and bone marrow biopsy appear hypocellular, with scant amounts of morphologically normal hematopoietic progenitors

Treatment

Medications

  • Antibiotics to treat infections

  • Immunosuppression with equine antithymocyte globulin (ATG) plus cyclosporine for severe aplastic anemia in adults aged > 40 or those without HLA-matched siblings

  • Useful regimen is equine ATG, 40 mg/kg/day intravenously for 4 days, in combination with cyclosporine, 6 mg/kg orally twice daily, given in hospital in conjunction with corticosteroids, and transfusion and antibiotic support

  • Corticosteroids are given with ATG (prednisone or methylprednisolone, 1–2 mg/kg/day orally for 1 week followed by taper over 2 weeks) to avoid ATG infusion reactions and serum sickness

  • Equine ATG is superior to rabbit ATG

  • Androgens (such as fluoxymesterone, 10–20 mg/day orally in divided doses)

    • Used widely used in the past, with a low response rate

    • May be considered in mild cases

    • Appear to partially correct telomere length maintenance defects

    • Appear to increase the production of endogenous erythropoietin

  • Eltrombopag

    • – A thrombopoietin ...

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