Internal Medicine Topic Review: Leukemia

Internal Medicine - USMLE Step 3 - Leukemia

The Four common types of Leukemia


Leukemia is a commonly tested topic on the ABIM exam and on other medical exams where internal medicine is a major focus. As you heard earlier this week, we’re really excited to get to share with you some of the gems out of the Cracking the USMLE Step 3… Today, as we continue along #OncWeek, we’re reviewing leukemias.


The following excerpt is taken directly from Cracking the USMLE Step 3.


Acute Myelogenous Leukemia (AML)
  • Signs and symptoms include:
    • Shortness of breath
    • Easy bruising and bleeding
    • Infection
    • Splenomegaly
  • May see Auer rods in peripheral smear
    • Red rod shaped structures in the cytoplasm of myeloblasts
  • Definitive diagnosis requires bone marrow biopsy
    • Greater than 20 % of the bone marrow infiltrated with myeloblasts
  • Positive myeloperoxidase
    • Differentiates AML from Acute Lymphocytic Leukemia (ALL)
    • Treatment involves chemotherapy with cytarabine
    • Bone marrow transplant is best treatment overall for remission
    • Several subtypes
      • Acute Promyelocytic Leukemia (APL)
        • Translocation of chromosomes 15 and 17
        • Treat with trans-retinoic acid
Acute Lymphocytic Leukemia (ALL)
  • Good prognosis (i.e., cure rate 85%)
  • Increased incidence in:
    • Down syndrome
    • Fanconi’s anemia
    • Ataxia-telangiectasia
    • Bruton’s agammaglobulinemia
  • Signs and symptoms include:
    • Infections
    • Enlarged lymph nodes
    • Splenomegaly
    • Petechiae
  • Diagnose initially with CBC
  • Peripheral smear shows blasts
  • Definitive diagnosis made with bone marrow biopsy definitive with blasts
  • Treat with chemotherapy
  Chronic Myelogenous Leukemia (CML)
  • Signs and symptoms include:
    • Gout
    • Infections
    • Easy bruising and bleeding
    • Splenomegaly
  • Philadelphia chromosome is key in diagnosis
    • Chromosomes 9 and 22 translocation
  • CML must be distinguished from leukemoid reaction
    • Leukemoid reaction has positive leukocyte alkaline phosphatase
    • CML negative for leukocyte alkaline phosphatase
  • Can evolve into a blast crisis
    • Greater than 20 % myeloblasts in the blood or bone marrow
  • Treat with imatinib (i.e., Gleevac), a tyrosine kinase inhibitor
Chronic Lymphocytic Leukemia (CLL)
  • Most common form of leukemia
  • May transform into Richter’s syndrome
    • Acute leukemia
  • Peripheral smear shows smudge cells
    • Cells are fragile when smeared onto glass slide
  • To definitively diagnosis, obtain bone marrow biopsy with flow cytometry to show markers CD19 and CD20 (i.e., B cell lineage markers)
  • If symptomatic, start with fludarabine
  • May also use rituxamab, an antibody against CD20 or alemtuzumab, an antibody against CD52·
Cracking the USMLE Step 3 is a leading textbook for USMLE Step 3 board exam preparation. The book was published in May 2012 and is available for sale online and at retailers nationwide.

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