Master the board step 3

Master the Boards: USMLE Step 3
Test for CML with
••
PCR, or
••
FISH
Diagnostic Testing
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An elevated neutrophils count with a low LAP score is CML. Reactive high
white counts from infection give an elevated LAP score. LAP is up in normal
cells, not CML.
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Most accurate test: Philadelphia chromosome by PCR of blood or BCR/ABL
by fluorescence in situ hybridization (FISH)
Treatment
The best initial therapy is imatinib (Gleevec). Bone marrow transplantation
is the only way to cure CML, but this is never the best initial therapy, because
imatinib leads to 90 percent hematologic remission with no major adverse
effects. Dasatinib and nilotinib are tyrosine kinase inhibitors. They can be used
as first-line therapy or as an alternative in those not responding to imatinib.
Following are wrong answers for CML treatment:
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Interferon: Much less efficacy; causes uncomfortable, flulike symptoms
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Hydroxyurea: Never makes the Philadelphia chromosome negative
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Busulfan: Never right for anything, unless the exam asks what causes pulmonary
fibrosis
Chronic Lymphocytic Leukemia (CLL)
CLL exclusively presents in patients > 50 years old with an elevated white
cell count that is described as “normal appearing lymphocytes.” CLL is often
asymptomatic and is described as being found on “routine” testing.
Diagnostic Testing
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Best initial test: Peripheral blood smear shows “smudge” cells, which are
ruptured nuclei of lymphocytes. They are like squished jelly donuts.
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Stage 0: Elevated white cell count alone
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Stage 1: Enlarged lymph nodes
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Stage 2: Spleen enlargement
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Stage 3: Anemia
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Stage 4: Low platelets
Basic Science Correlate
Mechanism of Infection and Hemolysis in CLL
The lymphocytes in CLL produce either abnormal or insufficient
immunoglobulins. When the IgG produced is abnormal, it is inappropriately
directed against RBCs or platelets, causing immune thrombocytopenia or
hemolysis. When IgG supply is insufficient, it leads to infection.
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