Chapter 102. Aplastic Anemia, Myelodysplasia, and Related Bone Marrow Failure Syndromes (Part 2)

Aplastic AnemiaDefinitionAplastic anemia is pancytopenia with bone marrow hypocellularity. Acquired aplastic anemia is distinguished from iatrogenic marrow aplasia, marrow hypocellularity after intensive cytotoxic chemotherapy for cancer. Aplastic anemia can also be constitutional: the genetic diseases Fanconis anemia and dyskeratosis congenita, while frequently associated with typical physical anomalies and the development of pancytopenia early in life, can also present as marrow failure in normal-appearing adults. Acquired aplastic anemia is often stereotypical in its manifestations, with the abrupt onset of low blood counts in a previously well young adult; seronegative hepatitis or a course of an incriminated medical drug may precede...
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Chapter 102. Aplastic Anemia, Myelodysplasia, and Related Bone Marrow Failure Syndromes (Part 2) Chapter 102. Aplastic Anemia, Myelodysplasia, and Related Bone Marrow Failure Syndromes (Part 2) Aplastic Anemia Definition Aplastic anemia is pancytopenia with bone marrow hypocellularity.Acquired aplastic anemia is distinguished from iatrogenic marrow aplasia, marrowhypocellularity after intensive cytotoxic chemotherapy for cancer. Aplastic anemiacan also be constitutional: the genetic diseases Fanconis anemia and dyskeratosiscongenita, while frequently associated with typical physical anomalies and thedevelopment of pancytopenia early in life, can also present as marrow failure innormal-appearing adults. Acquired aplastic anemia is often stereotypical in itsmanifestations, with the abrupt onset of low blood counts in a previously wellyoung adult; seronegative hepatitis or a course of an incriminated medical drugmay precede the onset. The diagnosis in these instances is uncomplicated.Sometimes blood count depression is moderate or incomplete, resulting in anemia,leukopenia, and thrombocytopenia in some combination. Aplastic anemia isrelated to both paroxysmal nocturnal hemoglobinuria (PNH; Chap. 101) and toMDS, and in some cases a clear distinction among these disorders may not bepossible. Epidemiology The incidence of acquired aplastic anemia in Europe and Israel is two casesper million persons annually. In Thailand and China, rates of five to seven permillion have been established. In general, men and women are affected with equalfrequency, but the age distribution is biphasic, with the major peak in the teens andtwenties and a second rise in the elderly. Etiology The origins of aplastic anemia have been inferred from several recurringclinical associations (Table 102-2); unfortunately, these relationships are notreliable in an individual patient and may not be etiologic. In addition, while mostcases of aplastic anemia are idiopathic, little other than history separates thesecases from those with a presumed etiology such as a drug exposure. Table 102-2 Classification of Aplastic Anemia and Single Cytopenias Acquired Inherited Aplastic Anemia Secondary Fanconis anemia Radiation Dyskeratosis congenita Drugs and chemicals Shwachman-Diamond syndrome Regular effects Reticular dysgenesis Idiosyncratic reactions Amegakaryocytic thrombocytopenia Viruses Familial aplastic anemias Epstein-Barr virus (infectious Preleukemia (monosomy 7,mononucleosis) etc.) Hepatitis (non-A, non-B, non-C Nonhematologic syndromehepatitis) (Downs, Dubowitz, Seckel) Parvovirus B19 (transient aplasticcrisis, PRCA) HIV-1 (AIDS) Immune diseases Eosinophilic fasciitis Hypoimmunoglobulinemia Thymoma/thymic carcinoma Graft-versus-host disease inimmunodeficiency Paroxysmal nocturnalhemoglobinuria PregnancyIdiopathicCytopeniasPRCA (see Table 102-4) Congenital PRCA (Diamond- Blackfan anemia)Neutropenia/Agranulocytosis Idiopathic Kostmanns Syndrome Drugs, toxins Shwachman-Diamond syndromePure white cell aplasia Reticular dysgenesisThrombocytopenia Drugs, toxins Amegakaryocytic thrombocytopenia Idiopathic amegakaryocytic Thrombocytopenia with absent radiiNote: PRCA, pure red cell aplasia.