Chapter 102. Aplastic Anemia, Myelodysplasia, and Related Bone Marrow Failure Syndromes (Part 14)

Bone Marrow The bone marrow is usually normal or hypercellular, but in 20% of cases it is sufficiently hypocellular to be confused with aplasia. No single characteristic feature of marrow morphology distinguishes MDS, but the following are commonly observed: dyserythropoietic changes (especially nuclear abnormalities) and ringed sideroblasts in the erythroid lineage; hypogranulation and hyposegmentation in granulocytic precursors, with an increase in myeloblasts; and megakaryocytes showing reduced numbers or disorganized nuclei. Megaloblastic nuclei associated with defective hemoglobinization in the erythroid lineage are common. Prognosis strongly correlates with the proportion of marrow blasts. Cytogenetic analysis and fluorescent in situ hybridization can...
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Chapter 102. Aplastic Anemia, Myelodysplasia, and Related Bone Marrow Failure Syndromes (Part 14) Chapter 102. Aplastic Anemia, Myelodysplasia, and Related Bone Marrow Failure Syndromes (Part 14) Bone Marrow The bone marrow is usually normal or hypercellular, but in 20% of cases itis sufficiently hypocellular to be confused with aplasia. No single characteristicfeature of marrow morphology distinguishes MDS, but the following arecommonly observed: dyserythropoietic changes (especially nuclear abnormalities)and ringed sideroblasts in the erythroid lineage; hypogranulation andhyposegmentation in granulocytic precursors, with an increase in myeloblasts; andmegakaryocytes showing reduced numbers or disorganized nuclei. Megaloblasticnuclei associated with defective hemoglobinization in the erythroid lineage arecommon. Prognosis strongly correlates with the proportion of marrow blasts.Cytogenetic analysis and fluorescent in situ hybridization can identifychromosomal abnormalities. Differential Diagnosis Deficiencies of vitamin B12 or folate should be excluded by appropriateblood tests; vitamin B6 deficiency can be assessed by a therapeutic trial ofpyridoxine if the bone marrow shows ringed sideroblasts. Marrow dysplasia canbe observed in acute viral infections, drug reactions, or chemical toxicity butshould be transient. More difficult are the distinctions between hypocellular MDSand aplasia or between refractory anemia with excess blasts and early acuteleukemia. The World Health Organization considers the presence of 20% blasts inthe marrow as the criterion that separates acute myeloid leukemia from MDS. Prognosis The median survival varies greatly from years for patients with 5q– orsideroblastic anemia to a few months in refractory anemia with excess blasts orsevere pancytopenia associated with monosomy 7; an International PrognosticScoring System (Table 102-6) assists in making predictions. Most patients die as aresult of complications of pancytopenia and not due to leukemic transformation;perhaps one-third will succumb to other diseases unrelated to their MDS.Precipitous worsening of pancytopenia, acquisition of new chromosomalabnormalities on serial cytogenetic determination, and increase in the number ofblasts are all poor prognostic indicators. The outlook in therapy-related MDS,regardless of type, is very poor, and most patients will progress within a fewmonths to refractory acute myeloid leukemia. Table 102-6 International Prognostic Scoring System Score Value Prognostic 0 0.5 1.0 1. 2.Variable 5 0 Bone Intermediat 0.5–e-1 1.0 Intermediat 1.5–e-2 2.0 High ≥2.5 a Good, normal, -Y, del(5q), del (20q); poor, complex (≥3 abnormalities) orchromosome 7 abnormalities; intermediate, all other abnormalities. b Cytopenias defined as Hb