OBJECTIVETo investigate NPM1 gene mutations in patients with primary myelodysplastic syndromes (MDS) and the clinical characteristics of patients with NPM1 mutants.

METHODSGenomic DNA corresponding to exon 12 of NPM1 gene was amplified by polymerase chain reaction (PCR) in 232 patients with primary MDS. Identification of mutants was by direct sequencing and classification of mutation types by sequencing followed by plasmid cloning.

RESULTSNPM1 mutants were found in 9 patients (3.9%). All the mutants were type A. As compared with those with NPM1 wild type, patients with the mutant were of lower ANC \[0.60 (0.12 - 2.91) × 10(9)/L vs 1.02 (0 - 10.23) × 10(9)/L, P = 0.046\], higher blast percent in bone marrow \[0.050 (0 - 0.090) vs 0.025 (0 - 0.190), P = 0.035\], decreased BFU-E \[0 (0 - 0)/10(5) BMMNC vs 6 (0 - 40)/10(5) BMMNC, P = 0.038\] and increased serum vitamin B(12) \[936.40 (373.80 - 2400.00) pmol/L vs 557.85 (17.00 - 3032.10) pmol/L, P = 0.045\] The chromosomal karyotypes of patients with NPM1 mutant were predominantly normal.

CONCLUSIONMDS patients with NPM1 gene mutations have some unique clinical and laboratory features. The results give new hint for the pathogenesis of MDS development and progression.