Patty, when my platelet count rose slowly & steadily over several years I was very worried about the possible cause (inflammation? infection? ovarian cancer?). When it reached 400-500 about 6 months ago, genetic testing showed the JAK2 mutation. I believe that's present in many (maybe most?) ET cases & that (I think) was likely the cause. Started taking one 500 HU a day & the numbers are now in the normal range -- hoping they stay there.

Jean