Cases with low levelJAK2V617F mutations are increasingly detected; however, the clinical interpretation of the low alleleJAK2burden may be challenging. The aim of this study is to analyze and compare the bone marrow morphology and peripheral blood findings in the low levelJAK2V617F allele burden (≤15% ofJAK2) and highJAK2V617F mutation burden patients (>15%JAK2). In total, 122JAK2V617F positive cases with concomitant bone marrow biopsies and peripheral blood findings were re-evaluated (62 low and 60 high levelJAK2V617F positive). Within the low burden group, normal looking megakaryocytes (p= 0.0005) were more frequently found, compared with those with no atypia (p= 0.0003), their number was more frequently not increased (p= 0.009), and they did not form clusters (p= 0.001). We found statistically significant difference in the number of platelet (p= 0.0003) and hematocrit levels (p= 0.032) when comparing theJAK2V617F <3% and ≥3% mutation burden. In the high-level burden, the megakaryocytes were more frequently atypical (p= 0.054), and more frequently formed clusters (p= 0.053) with nuclei with maturation defects (p≤ 0.0001). In conclusion, theJAK2V617F mutation burden is reflected by morphological changes in the bone marrow and careful follow up of each and every patient with a lowJAK2V617F positivity is mandatory.