USMLE Step 1

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Biochemistry

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Leukemias and Lymphomas

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Chronic Myelogenous Leukemia (CML)

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Summary

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Key Points

  • Chronic Myelogenous Leukemia (CML)
    • Etiology
      • t(9;22) or Philadelphia chromosome creates BCR-ABL fusion gene
        • Diagnosis of CML requires presence of BCR-ABL fusion gene
    • Presentation
      • Affects older adults
        • Median age of diagnosis is 64 years old
      • Increased levels of mature granulocytes: neutrophils, metamyelocytes, myelocytes, esp basophils
        • Due to myeloid stem cell proliferation
        • Very few blast cells are usually seen
      • Very low LAP (leukocyte alkaline phosphatase)
        • Result of low activity in malignant neutrophils
        • Contrast vs. leukemoid reaction (e.g. infection) where LAP is high
      • May accelerate and transform to AML or ALL (“blast crisis”)
    • Treatment
      • Imatinib or Dasatinib
        • Targeted BCR-ABL inhibitors