[Secondary and primary thrombocythemia]

Reactive thrombocytosis is an elevation of platelet count occurring in association with certain underlying diseases such as various infections, inflammatory, neoplastic and asplenic states. Essential thrombocythemia is a myeloproliferative syndrome affecting megakaryocytes, which leads to increased numbers of circulating platelets. This disorder is characterized by splenomegaly and a clinical course punctuated by hemorrhagic and/or thrombotic episodes.