Some families do have several members with ET or another MPN. Researchers think that the mutation itself is not inherited, but possibly a tendency to mutate if exposed to the same triggers is inherited.

Some decreases in platelets are not significant. Docs are looking at the average over a year or two. Mine usually stay between 415 to 475. Once every year or two, I might spike into low 500s. If counts stayed in the 500s and started spiking into the 600s, I expect my HU dose would be increased.

But the docs are looking at where your platelets are trending over time, not worrying about small up-and-down fluctuations.

I don't know what kind of drop in platelets you're seeing.