The bone marrow fibrosis observed in primary myelofibrosis is due ...

[K@]

The bone marrow fibrosis observed in primary myelofibrosis is due to:
 
  a. Malignant proliferation of fibroblasts
  b. Increased erythropoietin, which stimulates fibroblast proliferation
  c. Increased release of fibroblastic growth factors such as platelet-derived growth factor
  d. Decreased apoptosis of normal fibroblasts

Question 2

The Philadelphia chromosome:
 
  a. Is a balanced reciprocal translocation between chromosomes 7 and 19
  b. Results in a chimeric gene (bcr/abl)
  c. Is diagnostic for polycythemia vera
  d. Manifests as a tyrosine kinase that blocks cell maturation

[jaykayy05]

Answer to Question 1

ANS: C
An increased release of fibroblastic growth factors occurs, including platelet-derived growth factor, in primary myelofibrosis; this results in fibrosis. The fibroblasts in primary myelofibrosis are normal, not malignant.

Answer to Question 2

ANS: B
The Philadelphia chromosome results in the chimeric gene bcr/abl. It is a balanced reciprocal translocation between chromosomes 22 and 9. This chimeric gene manifests as a tyrosine kinase (P210), which appears to induce clonal cell proliferation. Although it affects maturation, as well as proliferation, it results in increased numbers of mature granulocytes in peripheral blood, so it does not block cell maturation.