American Board of Internal Medicine (ABIM) Certification Practice Exam

What genetic abnormality should be tested for in patients with suspected chronic myeloid leukemia?

1. JAK2 mutation

2. Philadelphia chromosome

3. BCR-ABL

4. TP53 mutation

The correct answer is: BCR-ABL

Chronic myeloid leukemia (CML) is commonly associated with a specific genetic abnormality, the BCR-ABL fusion gene, which results from a translocation between chromosomes 9 and 22. This genetic alteration is a hallmark of CML and is pivotal both for diagnosis and for monitoring the disease. The presence of the BCR-ABL fusion gene indicates the activation of tyrosine kinase signaling pathways that contribute to the pathogenesis of the disease. Testing for this specific genetic marker is essential because it not only confirms the diagnosis of CML but also informs treatment decisions. For instance, patients with the BCR-ABL fusion can be treated effectively with targeted therapies such as tyrosine kinase inhibitors, which have significantly improved outcomes. In contrast, while the Philadelphia chromosome is often discussed in relation to CML, it is important to note that the BCR-ABL fusion is the key functional abnormality derived from this chromosome. The other options, such as the JAK2 mutation and TP53 mutations, are associated with other hematologic disorders and malignancies rather than CML specifically. Therefore, confirming the presence of the BCR-ABL fusion is crucial in the context of suspected chronic myeloid leukemia.