Review Question - QID 102776

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Chronic Myeloid Leukemia (CML) ETIOLOGY Pathogenesis QID: 102776 (M3.ON.12.22)

QID 102776 (Type "102776" in App Search)

A 61-year-old woman presents to your office complaining of mild fatigue and weight loss over the past 6 months. She states she has felt generally unwell and has had decreased appetite during this time frame. Her temperature is 98.1°F (36.7°C), blood pressure is 122/80 mmHg, pulse is 88/min, respirations are 16/min, and oxygen saturation is 98% on room air. Physical exam reveals splenomegaly and a nontender abdomen. A complete blood count with differential shows the following:

Hemoglobin: 10 g/dL
Hematocrit: 30%
Leukocyte count: 166,500/mm^3
Segmented neutrophils 92%
Leukocyte alkaline phosphatase: Low
Platelet count: 92,000/mm^3

A bone marrow biopsy is performed demonstrating infiltration with a large number of normal-appearing neutrophils. Which of the following translocations is likely to be seen in this patient?

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t(8;14)

1/22

t(9;22)

32%

7/22

t(12;21)

1/22

t(14;17)

41%

9/22

t(15;17)

0/22

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This patient has chronic myelogenous leukemia (CML) given her splenomegaly, weight loss, increased leukocyte count with a neutrophil predominance, and biopsy demonstrating neutrophil infiltration. CML is associated with a t(9;22) translocation.

CML is a myeloproliferative neoplasm characterized by clonal overproduction of hematopoietic myeloid stem cells that can differentiate. The median age at presentation is 50. The disease has 3 clinical phases:

1) Chronic phase: fatigue, splenomegaly, malaise, weight loss, night sweats, and abdominal fullness
2) Accelerated phase: refractory leukocytosis and worsening symptoms including bone pain, bleeding, infections, and pruritis
3) Blastic phase: WBC > 100,000/mL with severe constitutional symptoms

The presence of a (9;22) translocation to form the Philadelphia chromosome is common in CML. The translocation results in the formation of the BCR-ABL fusion protein which possesses unregulated tyrosine kinase activity. Tyrosine kinase inhibitors (such as imantinib) are therefore first-line treatment for CML. Allogeneic hematopoietic stem cell transplant is used to treat patients with an available donor who present in the accelerated or blastic phase or who are refractory to imatinib.

Incorrect Answers:
Answer 1: t(8;14) is characteristic of Burkitt lymphoma which presents with a jaw or abdominal mass and is associated with Epstein-Barr virus.

Answer 2: t(14;17) is associated with acute promyelocytic leukemia in some cases but is a less frequently tested translocation.

Answer 3: t(12;21) is characteristic of acute lymphoblastic leukemia (ALL) which presents with pancytopenia, anemia, fatigue, leukopenia, and thrombocytopenia. Other translocations that can be seen in this condition include 9:22 which is associated with a poor prognosis.

Answer 5: t(15;17) is characteristic of acute promyelocytic leukemia which can present with hemorrhage and DIC. The treatment is all-trans-retinoic acid.

Bullet Summary:
The 9:22 translocation forms the Philadelphia chromosome in CML.

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