CO59 | JAK2 46/1 haplotype and JAK2 variant allelic frequency correlate with the development of polycythemic phenotype in JAK2-mutated essential thrombocytemia patients

Appearance of a polycythemic phenotype (PP) in patients (pts) with JAK2 mutated Essential Thrombocythemia (ET) strictly diagnosed according to ICC/WHO criteria represents an uncommon occurrence. The JAK2 46/1 (GGCC) haplotype (46/1), spanning 250–280 Kb on chr9p24.1, has been associated with higher blood counts and the acquisition of JAK2V617F homozygosity. We investigated clinical and molecular features of ET pts who developed PP, focusing on potential role of 46/1 and JAK2V617F variant allele frequency (VAF), that in turn was reported positively associated with higher hemoglobin levels.