12th Congress of the European Hematology ... - Haematologica

0897
THE PHENOTYPE OF JAK2V617F MUTANT PATIENTS WITH ESSENTIAL THROMBOCYTHEMIA
IS NOT RELATED TO THE BURDEN OF MUTANT ALLELE
E. Antonioli, 1 P. Guglielmelli, 2 G. Poli, 2 G. Longo, 2 V. Ponziani, 2
A. Pancrazzi, 2 A. Bosi, 2 A.M. Vannucchi 2
1 University of Florence, FLORENCE; 2 Dept Hematology, University of Florence,
FLORENCE, Italy
Background. The correlation of JAK2V617F mutation with clinical phenotype
of Ph-cMPD patients is still under debate, in part because of heterogeneity
of available series and of a discontinuous (hetero vs homo) rather
than continuous quantitative approach to mutational load. Aims. As an
approach to unravel significant associations between phenotype and
JAK2 mutation, we have correlated the levels of JAK2V617F allele load
with clinical and laboratory characteristics at diagnosis in a series of
patients with essential thrombocythemia (ET). Methods. 223 patients with
ET, diagnosed according to PVSG or WHO criteria, were studied. Median
age was 51 years (range, 16-93). JAK2V617F allele ratio was evaluated
at diagnosis by a Taqman one-step assay on granulocytes DNA. Results.
142 patients (64%) were JAK2V617F mutant, among which 92% presented
levels of mutated allele between 1% to 50% (corresponding to an
heterozygous status) and 8% higher than 50% (homozygous status),
accounting for 58% and 5% of patient population, respectively. Median
level of mutant JAK2 allele was 20% (range 1-87%), that is significantly
lower than the level found in a population of PV patients (n=135; 54%,
range 1-100; p