Aplastic Anemia

Basics

Description

Aplastic anemia represents a heterogenous group of disorders characterized by peripheral pancytopenia and bone marrow hypocellularity.

Epidemiology

Incidence

  • Estimated incidence of 2:1,000,000 per year in Western Hemisphere and Europe with increased incidence of 5 to 7:1,000,000 per year in Far East and those of Asian descent
  • In the pediatric population, most commonly presents between ages 15 and 25 years

Risk Factors

Genetics

Patients with a number of inherited bone marrow failure syndromes are at increased risk of developing aplastic anemia. Recent evidence implicates somatic clonal mutations of genes involved in immune regulation and cellular proliferation in acquired aplastic anemia.

General Prevention

Aside from avoidance of environmental toxins (as described below), there are no practical preventive measures for acquired aplastic anemia.

Pathophysiology

  • Most instances of acquired aplastic anemia are thought to occur through a T-cell dependent autoimmune process leading to apoptosis of hematopoietic stem or progenitor cells.
  • Additionally, exposure to certain toxins, chemicals, medications (classically chloramphenicol), and high doses of radiation can also lead to marrow aplasia.

Etiology

Acquired

  • Idiopathic (70% of cases)
  • Toxin: exposure to arsenic, benzene, radiation, organophosphates, organochlorines
  • Drugs: chloramphenicol, numerous chemotherapeutic agents
  • Radiation
  • Paroxysmal nocturnal hemoglobinuria (PNH)
  • Seronegative hepatitis (non-A, non-B, and non-C)
  • HIV-1, Epstein-Barr virus (EBV), human herpes virus 6 (HHV-6), cytomegalovirus (CMV)
  • Malnutrition
  • Pregnancy

Commonly Associated Conditions

  • Congenital or inherited bone marrow failure syndromes
    • Fanconi anemia, Shwachman-Diamond syndrome, Diamond-Blackfan anemia, dyskeratosis congenita, congenital amegakaryocytic thrombocytopenia, germline GATA2 mutations, Pearson syndrome
  • Acquired
    • Differentiating aplastic anemia from refractory cytopenia of childhood (RCC) is crucial as RCC is considered a form of myelodysplastic syndrome (MDS) and should be considered for hematopoietic stem cell transplantation (HSCT).

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