Original Article Diagnostic Hematology

Background: Calreticulin (CALR) mutations were recently discovered in patients with my-eloproliferative neoplasms (MPNs). We studied the frequency and type of CALR mutations and their hematological characteristics. Methods: A total of 168 MPN patients (36 polycythemia vera [PV], 114 essential throm-bocythemia [ET], and 18 primary myelofibrosis [PMF] cases) were included in the study. CALR mutation was analyzed by the direct sequencing method. Results: CALR mutations were detected in 21.9 % of ET and 16.7 % of PMF patients, which accounted for 58.5 % and 33.3 % of ET and PMF patients without Janus kinase 2 (JAK2) or myeloproliferative leukemia virus oncogenes (MPL) mutations, respectively. A total of five types of mutation were detected, among which, L367fs*46 (53.6%) and K385fs*47 (35.7%) were found to be the most common. ET patients with CALR mutation had lower leukocyte counts and ages compared with JAK2-mutated ET patients. Conclusion: Genotyping for CALR could be a useful diagnostic tool for JAK2-or MPL-neg-ative ET or PMF patients. CALR mutation may be a distinct disease group, with different hematological characteristics than that of JAK2-positive patients