thrombocytosis

noun

throm·​bo·​cy·​to·​sis ˌthräm-bə-ˌsī-ˈtō-səs 

plural thrombocytoses -ˈtō-sēz 

: increase and especially abnormal increase in the number of platelets in the blood that typically occurs in association with a myeloproliferative disorder (as thrombocythemia or chronic myelogenous leukemia) or as a nonspecific response to an underlying disorder or disease (as a systemic infection)

also : thrombocythemia