Review Question - QID 212486

This patient with fatigue, pallor, and dacrocytes on peripheral blood smear most likely has myelofibrosis, which is associated with increased production of platelet-derived growth factor.

Myelofibrosis can present with anemia or bleeding in older adults in the 5th and 6th decades of life. It is caused by a neoplasia of mature myeloid cells such as megakaryocytes with a mutation in the JAK2 kinase protein. This neoplastic development can lead to anemia because megakaryocyte hyperplasia results in increased production of platelet-derived growth factor. Signaling downstream of this factor results in fibrotic obliteration of the bone marrow. Therefore, a decrease in all 3 hematopoetic cell lines can be observed. Importantly, myelofibrosis is associated with teardrop-shaped red blood cells known as dacrocytes on peripheral blood smear.

Figure A shows a peripheral blood smear with teardrop-shaped red blood cells known as dacrocytes, which is classically associated with myelofibrosis.

Incorrect Answers:
Answer 1: Abnormal triglyceride handling is associated with abetalipoproteinemia, which would present with spur cells known as acanthocytes rather than dacrocytes.

Answer 3: Inhibition of metalloproteinase activity is associated with thrombotic thrombocytopenic purpura, which would present with helmet-shaped schistocytes rather than dacrocytes.

Answer 4: Mutation in cytoskeletal proteins is associated with hereditary spherocytosis, which would present with spherocytes rather than dacrocytes.

Answer 5: Mutation in glycolysis pathway proteins such as pyruvate kinase is associated with anemia that presents with echinocytes (burr cells) rather than dacrocytes.

Bullet Summary:
Myelofibrosis will lead to anemia with teardrop-shaped red blood cells known as dacrocytes.