LabMed

Idiopathic Aplastic Anemia

At a Glance

Idiopathic aplastic anemia is an acquired bone marrow failure syndrome. It presents with the sequelae of peripheral cytopenias. Patients may exhibit fatigue, pallor, dyspnea on exertion, tachycardia due to anemia, and easy bruising or mucocutaneous bleeding due to thrombocytopenia. Patients may also present with infections due to leukopenia. Aplastic anemia can occur at any age, but it is particularly common in adolescents and young adults, with a second incidence peak in the elderly population.

What Tests Should I Request to Confirm My Clinical Dx? In addition, what follow-up tests might be useful?

A complete blood count (CBC) with differential should be ordered to confirm the presence of cytopenias. Cytopenias of at least 2 lineages are required to consider a diagnosis of aplastic anemia.

Diagnosis of aplastic anemia requires confirmation of bone marrow hypocellularity by bone marrow aspirate and biopsy. Cytogenetic and flow cytometric analyses should be performed on the bone marrow aspirate to help exclude other causes of bone marrow failure.

Aplastic anemia is sometimes associated with paroxysmal nocturnal hemoglobinuria (PNH). Thus, peripheral blood should be submitted for PNH evaluation by flow cytometry.(Table 1)

Table 1.

Test Results Indicative of the Disorder
Hemoglobin Platelet count Absolute neutrophil count
<10 g/dL <100x109/L <1.5x109/L

Are There Any Factors That Might Affect the Lab Results? In particular, does your patient take any medications - OTC drugs or Herbals - that might affect the lab results?

Idiopathic aplastic anemia is a diagnosis of exclusion. Thus, other causes of bone marrow failure should be considered and ruled out, such as medication effects, including cytotoxic chemotherapy and drug-induced neutropenia, toxic insults, infectious processes, autoimmune disorders, and malignancies (see also bone marrow hypoplasia from bone marrow suppression and bone marrow replacement). Younger patients should be evaluated for congenital bone marrow failure syndromes, such as Fanconi's anemia, dyskeratosis congenita, and Shwachman-Diamond syndrome. Diagnostic considerations in older patients should include myelodysplastic syndrome and other hematologic malignancies.

What Lab Results Are Absolutely Confirmatory?

Confirmation of aplastic anemia requires bone marrow aspirate and core biopsy. The biopsy should be hypocellular for the patient's age and is often markedly so. Careful morphologic examination by a trained pathologist can rule out some alternative causes of bone marrow failure. In addition, flow cytometry performed on a bone marrow aspirate can exclude involvement by hematologic malignancies, such as leukemia and lymphoma. The presence of clonal cytogenetic abnormalities is usually an indication of a hematologic malignancy, such as myelodysplastic syndrome, leukemia, or lymphoma.

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