MPN PV different than ET

[neela2020]

In short MPN patients has to deal with haematocrit as well as platelets. That means ET is subpart of PV?? Do all PV patients has to deal with rising platelets?

[Manouche]

Not all. About 50% of PV patients are diagnosed with an above normal platelet level.

[Chaz1]

Same answer, no not all PV patients have a high platelet count. Not sure why it works out that some do. I've not looked into tbh.

[Ebot]

I understand that they are quite distinct. The sense from early on was that MPNs were a collection of diseases with distinct as well as shared characteristics. But it seems each patient’s profile is unique and there are lots of variants in terms of mutations, counts, symptoms etc.

Some people like me with PV have both a high platelet count and a high haematocrit count. Interestingly my initial diagnosis was an Unclassified MPN treated as ET as I had a high (and climbing) platelet count. The abnormal haematocrit levels did not reveal themselves until some years down the line when a second bone marrow biopsy confirmed PV.

[Kari1961]

As above - although I have PV Jak2+ and have never had a high platelet count, it's always been normal. With me it's high haematocrit alone.

[Johnsb]

In my case I have PV and no platelet count issues. There are some that have ET and a normal Hct level. Go figure. When I hear PV I think HCT/Hgb and when I hear EV I think platelets. For some people, it will stay that way and for others it will progress over time where both Hgb and Platelets go up.

Good Luck

[hunter5582]

The terms are a bit confusing at times.

Thrombocytosis = too many platelets

Erythrocytosis = too many red blood cells (erythrocytes)

Leukocytosis = too many white blood cells (leukocytes)

If you trade the "cytosis" for a "penia" it = "not enough" (e.g. erythropenia = not enough red blood cells).

Essential Thrombocythemia (aka Essential Thrombocytosis) = consistent elevated platelet levels (greater than 450K ) not due to another medical condition.

Polycythemia Vera = elevated erythrocytes not due to another medical condition. It may or may not be accompanied by thrombocytosis and/or leukocytosis. Docs tend to focus on the Hematocrit (HCT) as it is a good shorthand for what needs to be monitored. Note: the combination of erythrocytosis or leukocytosis with thrombocytosis increases the risk of thrombosis in PV patients. That is why controlling the HCT is so important.

JAK2 - Janus Kinase 2 gene. Mutation of this gene is one of the driver mutations that causes MPNs. It affects the JAK-STAT pathway, which is a tyrosine kinase system in your body. The JAK-STAT pathway regulates many things, including hematopoiesis (making blood cells), inflammation - inflammatory cytokine production, tumorigenesis, and apoptosis (regulated cell death). The disruption of the JAK-STAT pathway leads to a propensity for "Neoplasm - a new and abnormal growth of tissue in some part of the body, especially as a characteristic of cancer." "Myeloproliferative - relating to, or being a disorder (such as ET, PV, MF ML) marked by excessive proliferation of bone marrow elements and especially blood cell precursors." The short version is that the JAK2 mutation causes your body to overactivate hemopoietic stem cell production, the cells that make all other blood cells. This can play out in different ways in different people - hence the range of MPNs.

The line between ET and PV is not clear and distinct. It is more like a continuum of disorders. Sometimes you will see a diagnosis like "Chronic myeloproliferative disease" when the ET-PV distinction is not clear.

Hope that helps

[KnitEatCrochetRepeat in reply to hunter5582]

My understanding of the situation is that there is one type of cell that is out of control, this determines which MPN you have. As the person above has explained, it is possible to have several cells type go awry, creating a continuum of each MPN, but I'm not sure how common that is.

However, even when only one type of cell is affected (platelets for ET or red blood cells for PV), the overproduction of one cell can have a knock-on effect on production of others. The bone marrow gets crowded, and there isn't space to make all the ones you need. If there isn't room in the bone marrow for your stem cells to divide into blood cells, you can't make the normal cells either.

Hope that helps!

[Paul_1971]

No they dont but it does happen. Sometimes you will see people are diagnosed as having PV and ET although i suspect its just PV with elevated platelets. I have PV but my platelets would sometimes be a little over the top end normal, although now I am on Rux keeping my platelets up is more of a challenge.