Distribution of the JAK2 mutation within MPD families. (A) Classification of families according to the JAK2 genotype. Families were divided into 3 groups: negative (genotype GG) for the JAK2 mutation, positive (genotype GT) for the JAK2 mutation, and heterogeneous, including patients with GG or GT genotypes within families. (B) Phenotypic spectrum within subgroups of MPD families. ▪ indicates PV or MMM; □,ET; ▦, PV or MMM and ET.