OBJECTIVETo explore the coexistence of ASXL1 and CALR gene mutations in patients with essential thrombocytheima (ET) and with primary myelofibrosis(PMF), and to compare the differences of clinical characteristics between ET and PMF patients carrying ASXL1 and CALR mutations, and ET and PMF patients carrying solitary gene mutation, and ET and PMF patients without any mutations.

METHODSThe mutations of ASXL1 gene at exon 12, CALR gene at exon 9 and MPL gene at exon 10 in 263 essential ET patients and 29 PMF patients were detected by PCR amplification followed by direct sequencing of genomic DNA. The JAK2V617F mutations were used by allele specific PCR detection.

RESULTS72.6%(212/292)of patients harbored at least one mutation. The incidences of ASXL1 and CALR mutations were 5.8% and 30.5%, respectively. The frequencies of JAK2V617F and MPL mutations were 39.0% and 2.4%, respectively. 5.1%(15/292) of patients had double mutations, including ASXL1 and CALR(n=11), ASXL1 and JAK2V617F(n=2), MPL and CALR(n=1) and ASXL1 and MPL(n=1). The frequency of concurrent ASXL1 and CALR mutations was found to be high. Significant difference was found on hemoglobin levels and platelet counts between CALR and ASXL1 mutations and single mutation (P<0.05),however, the difference on leukocyte counts and median age was not found. Compared with negative patients, the presence of ASXL1 and CALR mutations was found to be significantly correlative with lower hemoglobin level (P=0.045), lower leukocyte count (P=0.002) and with higher platelet counts(P=0.001), but the difference of median age was not found.

CONCLUSIONThe frequency of concurrent ASXL1 and CALR mutations is higher in ET patients. The coexistence of ASXL1 and CALR gene mutations significantly associated with lower hemoglobin level and higher platelet count.