OBJECTIVETo explore the prevalence of CARL gene mutations and the mutation types in patients with essential thrombocythemia (ET), and to compare the patients clinical characteristics of CALR mutation with JAK2 V617F, MPL W515K mutation patients and triple negative group.

METHODSThe mutations of CALR gene at extron 9 and MPL W515K in 150 ET patients were detected by PCR amplification followed by direct sequencing of genomic DNA, the JAK2 V617F mutation by using allele specific PCR.

RESULTS(1)The CALR mutations were found in 38 patients (25.3%) of 150 ET patients. A total of 4 types of CALR mutations were identified (type Ic.1092_1143del52bp, n=17; type II c.1154_1155insTTGTC, n=16; type III c.1094_1139del46bp, n=4; type IV c.1103_1136del34bp, n=1). (2)The incidence of JAK2 V617F and MPL W515K was 61.3% (92/150) and 2.7% (4/150), respectively. The frequency of CALR mutation was 70.4% (38/54) in 54 ET patients without JAK2 V617F and MPL W515K mutations. The co-occurrence of any two kinds of gene mutations was not detected. (3)The hemoglobin level and leukocyte counts of patients with CARL mutations were significantly lower than that in patients with JAK2 V617F mutations (P<0.05). The median age of patients with CALR mutation was significantly higher than that of triple negative patients (59 years vs 29.5 years, P<0.01). Cytogenetic analysis was performed in 147 patients, and there were 4 abnormal karyotype cases. CALR mutation incidence was significantly higher in abnormal karyotype cases than that in normal ones (75% vs 24.5%, P=0.019).

CONCLUSIONThe incidence of CALR mutations is high in ET patients without JAK2 V617F and MPL W515K mutations, and is associated with abnormal karyotype. CARL-mutated cases showed a significantly lower leucocyte and hemoglobin levels compared with JAK2 V617F mutated cases.