Dear Doctor,

Due to my father's high blood viscosity, suspicion of polycythemia arises, necessitating blood draws every 3 weeks to maintain appropriate levels. At 69 years old, he experiences symptoms such as skin itching, swelling, head numbness, and fatigue. Currently, his JAK2 V617F mutation showed 0.8 then 1.2%, with JAK2 exon 12 negative and EPO at 13.4. Abdominal CT and chest X-ray are normal. After a few months of phlebotomy, his levels normalized. Now, we await the bone marrow biopsy results, which do not confirm Polycythemia Vera:
"Microscopic description:
The bone marrow biopsy sample shows somewhat hypocellular hematopoietic parenchyma relative to age, which is terminally mature. Myeloid
ratio is 2:1 with dominance of late precursors; no blast cells are noted. The number of megakaryocytes is normal with no clustering. There is no interstitial fibrosis or lymphoid infiltrate.
Diagnosis:
Mature, hypocellular hematopoietic parenchyma without myeloproliferative features.
Cytogenetic analysis confirmed male karyotype; no clonal chromosomal abnormalities detected.
Indication for examination D7510 Secondary polycythemia
Note Submicroscopic rearrangements, small structural chromosomal aberrations, DNA-level differences cannot be ruled out with the method used."

I am quite confused as JAK2 positivity typically suggests PV, yet the biopsy suggests otherwise, possibly indicating secondary polycythemia. Could you please clarify based on this information what you personally think is more likely, Polycythemia Vera or another secondary cause? Thank you very much for your help.