OBJECTIVETo analyze the CARL gene mutation in the patients with chronic myeloproliferative neoplasm(MPN) and to explore the clinical significance of CALR mutation.

METHODSThe peripheral blood of patients was collected and the genomic DNA was exacted, the 9 exon of CALR gene and the fragment of human thrombopoetic receptor(MPL) gene were amplified by PCR, the mutation of CALR and MPL genes was detected by using the direct sequencing, the JAK2 V617F mutation was detected by using allele spicific PCR.

RESULTSThe CALR mutations were detected in 13 patients out of 55 MPN patients (23.6%). The frequency of CALR mutation was 22.7% (10/44) in 44 essential thrombocythemia(ET) patients. A total of 3 types of CALR mutation were identified (type I c.1092_1143del52bp, n=5; type II c.1154_1155insTTGTC, n=4; type III c.1094_1139del46bp, n=1). CALR mutations occurred at a frequency of 27.2% in primary myelofibrosis (PMF), including type I (n=2) and type II (n=1). The incidence of JAK2 V617F was 58.1%(32/55), that in ET and PMF was 59.1%(26/44) and 54.5% (6/11), respectively. The mutations of MPL W515 were not detectable in all cases, and the simultaneous mutation of CARL and MPL W515 was not detected. The median age of patients with CALR mutation was significantly younger than that of patients with JAK2 mutations (48 vs 64 years of old, P<0.05). The levels of hemoglobin and leukocytes in patients with CARL mutations were significantly lower (P<0.05) but the level of plateletes was higher than that in patients with JAK2 V617F mutations (P<0.05). Deep venous thrombosis occurred in 4 of 35 ET patients with the JAK2 V617F mutation (n=4), but did not occurr in the patients with CALR mutation. Karyotype abnormality was detected in only one case among 48 patients by chromosome karyotype analysis.

CONCLUSIONThe incidence of CALR mutation is high in ET and PMF patients without JAK2 V617F and MPL W515K mutations, which is associated with younger median age, lower leucocyte and hemoglobin levels, higher platelet counts, and rare thrombocytosis, compared with the patients with JAK2 V617F mutation.