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INTRODUCTION

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CASE HISTORY • Part 1

A 28-year-old man, previously in excellent health, presents with a 2-week history of fatigue and worsening fever. He has been convinced by his family to seek medical attention because of noticeable pallor and the recent onset of a petechial rash on his extremities. His physical examination is remarkable for pallor, the petechial rash, pharyngitis, and gingivitis. He does not have lymphadenopathy or hepatosplenomegaly, and the remainder of the examination is unremarkable.

CBC: Hematocrit 19% WBC 32,000/μL

Differential: Neutrophils - 0% Monocytes - 2%

Lymphocytes - 13% Cells identified by an automated counter as immature - 85%

Platelets: 14,000/μL

SMEAR MORPHOLOGY

Mature neutrophils are not seen. Platelets are markedly decreased, but red cell morphology is normal. The immature cells are large, with an open nuclear chromatin pattern, prominent nucleoli, and few granules. In rare cells, one or more red staining, rod-shaped objects can be found (Auer rods).

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Questions
  • What further history, examination, and laboratory evaluation is indicated?

  • What should be the pace of this workup?

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The acute myeloid leukemias (AMLs) are clonal malignancies that are characterized by the appearance of increased numbers of immature myeloid cells in the marrow and blood. The fundamental oncogenic event takes place at the level of a very early progenitor cell, which results in a leukemic stem cell with self-renewal and multipotential properties. Still, the malignant progeny are often capable of considerable differentiation. This has led to classification schemes that emphasize the morphologic characteristics of the cell, patterned after the classification of normal myeloid cells.

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AML can present as an acute, catastrophic illness in a patient who is otherwise healthy. Alternatively, it can be the final outcome of a myeloproliferative disease such as chronic myeloid leukemia, polycythemia vera, or primary myelofibrosis or a myelodysplastic syndrome (see Chapters 9, 13, and 19). Despite the differences in onset and morphologic appearance, the AMLs generally have a similar clinical presentation, prognosis, and treatment.

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The yearly estimated incidence of AML in the United States is 12,000 new cases, two-thirds of which will die from the disease. As shown in Figure 18-1, the incidence is clearly age related: most patients are adults, and the median age of onset is 70 years. In elderly patients, the disease frequently presents as evolution from a myelodysplastic syndrome, whereas in younger patients, de novo AML is more common.

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FIGURE 18-1

AML age-specific incidence rates: 1998–2002 (NCI-SEER program). The incidence of AML increases steadily with age. Most cases are seen in the sixth, seventh, and eighth decades.

Graphic Jump Location
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LEUKEMIA CLASSIFICATION

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The original classification scheme for AML was the French-American-British (FAB) system, which began as a purely morphologic classification. However, over the years it has been bolstered by immunohistochemical and immunologic data, using markers for different stages of myeloid ...

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