The bone marrow exam showed an overall increase in bone marrow cellularity with megakaryocytic hyperplasia, meaning an increase in platelet precursor cells. A few clusters of megakaryocytes were also seen and occasional giant megakaryocytes, but no real megakaryocyte dysplasia (abnormal megakaryocytes) was noted. Please see the bone marrow biopsy to the right depicting megakaryocytic hyperplasia. The large cells are megakaryocytes.
The genetic studies were very revealing. The results included:
- Philadelphia chromosome (bcr/abl fusion) negative
- JAK2 (janus activated kinase 2) - V617F mutation-positive
Thus the patient met many of the criteria for a diagnosis of Essential Thrombocythemia (ET), a myeloproliferative neoplasm (MPN). These criteria include:
- Negative for inflammatory markers
- Megakaryocytic hyperplasia of the bone marrow, without other cell lines, affected (helps rule out other MPNs)
- Philadelphia chromosome-negative
- Consistent platelet count greater than 450,000/μL
- JAK2-V617F mutation, which is common, although not exclusively found in ET.
Note that being negative for Philadelphia Chromosome helped rule out another MPN, Chronic Myeloid Leukemia, which can also have elevated platelet counts.
