A patient can present with a raised hemoglobin (Hb), raised white cell count (WCC) or leukocytosis, or raised platelet counts and in each case the causes of the abnormality have to be considered and investigated in order to arrive at the diagnosis. Each type of abnormality will be discussed and illustrative cases given. Cases presenting with simultaneous multiple raised cell counts will also be considered. Erythrocytosis An absolute or true erythrocytosis is present when the red cell mass is greater than 125% predicted for the patient's sex and body mass. The presence of an erythrocytosis is indicted by an Hb and/or a hematocrit (Hct) above the upper limit of normal. However, a raised Hb or Hct may not necessarily indicate that a true erythrocytosis is present. It may be necessary to formally measure the red cell mass in order to prove that there is a true erythrocytosis as opposed to an apparent erythrocytosis (where the Hct is raised but the red cell mass is within the reference range) or a relative erythrocytosis (where the Hct is raised but the red cell mass is within the reference range and the plasma volume reduced). In cases where the Hct is above 0.60% in a male or 0.56% in a woman the red cell mass is always elevated and formal measurement of the red cell mass is unnecessary to prove the point. Differential diagnosis of erythrocytosis An erythrocytosis can be primary where there is an intrinsic defect within the bone marrow compartment or secondary where something usually mediated by erythropoietin (EPO) is driving the red cell mass expansion. In each case the cause can be congenital or acquired. Table 1.1 lists all the causes of an erythrocytosis. Initial assessment of an undiagnosed patient with erythrocytosis The patient should be seen and the full blood picture (FBP) repeated to confirm that the abnormality is present. A careful history and examination should then be carried out considering the differential diagnosis. Having confirmed the erythrocytosis if a diagnosis of polycythemia vera (PV) seems a possibility, the next investigation indicated is a test for JAK2 mutations which, if positive, will confirm clonal disease. If PV does not seem likely then the next step would be to measure the EPO level. A low-level EPO suggests a primary defect in the EPO signaling pathway and this should then be investigated further.
|Title of host publication||Managing Myeloproliferative Neoplasms|
|Subtitle of host publication||A Case-Based Approach|
|Publisher||Reader, Cambridge University Press|
|Number of pages||8|
|Publication status||Published - 01 Jan 2016|
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