Clinical and molecular features of 2 pedigrees with hereditary thrombocytosis. (A) Filled symbols represent individuals with JAK2 germ-line mutations. Below each symbol is reported the JAK2 genotype with “N” indicating a normal allele, the age (years) at diagnosis for affected individuals or the age at last examination for asymptomatic relatives, and the platelet level (×10⁹/L). (B) Sequence electropherograms of the germ-line JAK2 mutations.