Therapeutic thrombocytapheresis for extreme thrombocytosis after chemotherapy in essential thrombocytosis

: Essential thrombocytosis (ET) is a chronic myeloproliferative neoplasm characterized by the presence of thrombocytosis and it can be complicated by thrombotic and/or hemorrhagic events. Treatment options include low-dose aspirin and cytoreductive agents such as hydroxyurea. In cases of extreme thrombocytosis, therapeutic thrombocytapheresis can be a useful procedure. We present a case of a 61-year-old-man previously diagnosed with CALR-mutated ET, who develop acute myeloid leukemia. When recovering after induction chemotherapy, he developed an extreme thrombocytosis up to 2337 × 109 /L regardless hydroxyurea was started. Two therapeutic trombocytapheresis were performed and anagrelide was added to cytoreductive regimen. Platelet count stabilized around 570 × 109 /L. Both procedures were performed with the Spectra Optia Apheresis System version 11.3 (Terumo BCT) and we decided to use a higher collection preference and lower collection speed than manufacturer's recommendations. Platelet count decreased from 2380 × 109 /L to 1035 × 109 /L in the first procedure and from 1813 × 109 /L to 768 × 109 in the second procedure. Platelet collection efficiency was calculated to be 110.3% and 86.1% in the first and second thrombocytapheresis, respectively. Therapeutic thrombocytapheresis with Spectra Optia is a safe and efficient therapy to treat patients with primary thrombocytosis while effect of cytoreductive agents is attained. Platelet collection efficiency was calculated to be higher than previously reported. We suggest that changes in technical parameters such as a deeper aspiration point and/or lower collection speed may increase procedure's efficiency.