tailieunhanh - Chapter 103. Polycythemia Vera and Other Myeloproliferative Diseases (Part 3)

Diagnosis When PV presents with erythrocytosis in combination with leukocytosis, thrombocytosis, or both, the diagnosis is apparent. However, when patients present with an elevated hemoglobin or hematocrit alone, or with thrombocytosis alone, the diagnostic evaluation is more complex because of the many diagnostic possibilities (Table 103-2). Furthermore, unless the hemoglobin level is ≥20 gm% (hematocrit ≥60%), it is not possible to distinguish PV from disorders causing plasma volume contraction. Uniquely in PV, an expanded plasma volume can mask an elevated red cell mass; thus, red cell mass and plasma volume determinations are mandatory to establish the presence of an absolute. | Chapter 103. Polycythemia Vera and Other Myeloproliferative Diseases Part 3 Diagnosis When PV presents with erythrocytosis in combination with leukocytosis thrombocytosis or both the diagnosis is apparent. However when patients present with an elevated hemoglobin or hematocrit alone or with thrombocytosis alone the diagnostic evaluation is more complex because of the many diagnostic possibilities Table 103-2 . Furthermore unless the hemoglobin level is 20 gm hematocrit 60 it is not possible to distinguish PV from disorders causing plasma volume contraction. Uniquely in PV an expanded plasma volume can mask an elevated red cell mass thus red cell mass and plasma volume determinations are mandatory to establish the presence of an absolute erythrocytosis and to distinguish this from relative erythrocytosis due to a reduction in plasma volume alone also known as stress or spurious erythrocytosis or Gaisböck s syndrome . This is true even in with the discovery of the JAK2 V617F mutation because not very patient with PV expresses this mutation while patients without PV do. Figure 58-18 illustrates a diagnostic algorithm for the evaluation of suspected erythrocytosis. Table 103-2 Causes of Erythrocytosis Relative erythrocytosis Hemoconcentration secondary to dehydration androgens or tobacco abuse Absolute erythrocytosis Hypoxia Carbon monoxide intoxication High affinity hemoglobin High altitude Pulmonary disease Right-to-left shunts Sleep-apnea syndrome Neurologic disease Renal disease Renal artery stenosis Focal sclerosing or membranous glomerulonephritis Renal transplantation Tumors Hypernephroma Hepatoma Cerebellar hemangioblastoma Uterine fibromyoma Adrenal tumors Meningioma Pheochromocytoma .