Pedigrees of the 4 families with the 598C> T mutation. Circles denote female family members, squares denote male family members, and symbols with a diagonal line indicate deceased family members. Black symbols indicate individuals with erythrocytosis and shaded symbols, nonerythrocytosis carriers for the 598C>T mutation. The genotype of individuals is indicated by wt (normal) and 598C>T for mutant. Hemoglobin level (g/L), PCV, red blood cell count (RBC), and Epo (mU/mL) values are given when known.