PLT 150 - 370 HIGH

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The abnormality chosen is:

THROMBOCYTHEMIA, a platelet count greater than 350,000 cells/microL. An elevation in the platelet count may be primary or secondary. Primary, or essential thrombocythemia, is a myeloproliferative disease characterized by an increased platelet count, megakaryocytic hyperplasia and a thrombotic or hemorrhagic tendency. This disorder generally occurs between the fifth and seventh decades of life, and it is the result of excessive platelet production with a normal platelet survival time. Diagnostic criteria for essential thrombocythemia include a normal RBC mass (this excludes polycythemia vera), the absence of the Philadelphia chromosome (Philadelphia chromosome is present in chronic myelogenous leukemia), and the absence of teardrop-shaped RBCs or marrow fibrosis (both of which are associated with myelofibrosis). The Janus Kinase 2 (JAK-2) mutation has been identified in 50% of patients with this disorder and may be detected using DNA sequencing or PCR technique; however, it is also present in patients with polycythemia vera.

Secondary thrombocythemia, which is the more common cause, results from an underlying disorder. Hemorrhage, malignancy, iron deficiency, and infections are common causes. Rebound thrombocythemia may occur after thrombocytopenia, especially when excessive alcohol ingestion is the underlying etiology.

Excessive platelet counts associated with chronic myeloproliferative disorders such as essential thrombocythemia, polycythemia vera, primary myelofibrosis, and less commonly, chronic myelogenous leukemia may respond to treatment with hydroxyurea. In secondary thrombocythemia, therapy consists of correcting or treating the underlying disease.