Thus, Randi et al. reported three out of the 89 (3.4%) children with a clinical diagnosis of ET and detectable JAK2-V617F mutation suffering from Budd Chiari syndrome (two cases) and cerebral vein thrombosis (one case), equaling 13% in the subgroup of children with clonal disease [12]. The gene discussed is JAK2; the disease is essential thrombocythemia.