Myeloproliferative disorders: Pathology review

A 70 year old female named Jenny is brought by her husband to the emergency department complaining of blurred vision and headache. Her face appears plethoric and her husband says that Jenny has been complaining of extreme itchiness after showers for the last few days. She has no significant past medical history. CBC shows increased hematocrit and slightly increased platelets. Uric acid is also increased. Next to Jenny, there’s a 65 year old male named Seth that came in with fatigue and progressive weight loss due to early satiety. Past medical history is unremarkable. Clinical examination reveals a very enlarged spleen. CBC shows pancytopenia and peripheral blood smear shows teardrop cells.

Both Jenny and Seth suffer from myeloproliferative neoplasms. These are a group of malignant neoplasms characterized by proliferation of the bone marrow cells from the myeloid lineage. That includes RBCs, platelets, as well as granulocytes, which include neutrophils, basophils, mast cells, and eosinophils. Each disorder can potentially cause proliferation of all of the myeloid cells, but they’re classified based on the dominant cell line involved. So there’s polycythemia vera, for RBCs, essential thrombocythemia for platelets, chronic myeloid leukemia, or CML, for granulocytes, and the odd one out, primary myelofibrosis, which doesn’t really have a dominant cell line, but instead is characterized by bone marrow fibrosis.

Okay, now CML is associated with the 9:22 translocation, which is when there’s fusion of the BCR gene on chromosome 22 and the ABL tyrosine kinase gene on chromosome 9. This is called the Philadelphia chromosome. Now, in this video, let’s focus on the myeloproliferative disorders that are not associated with Philadelphia chromosome, or the “Philadelphia chromosome negative myeloproliferative disorders,” like polycythemia vera, essential thrombocythemia, and primary myelofibrosis. All right, so let’s take a closer look at these myeloproliferative disorders, starting with polycythemia vera, where there’s an increase in RBC production. It typically begins with a mutation in a single hematopoietic stem cell, which gives rise to RBCs, WBCs, and platelets.