Interesting, since that's exactly what happened after I started Jakafi. My platelets doubled in one week from 510-1100 (after just a couple weeks and stopping hydroxyurea). Doctor added hydroxyurea back in to hopefully control the platelets until Jakafi kicks in, and increased JK dose to 15mg 2x/day. Almost a month in, I feel worse than I did while on hydroxyurea which had minimal side effects for me, though my PV symptom of itchy skin didn't improve, which is why the switch to JK (still no improvement on itchiness).