Erythrocytosis was inherited as an autosomal trait, affecting 26 individuals, including children, in 3 families. The affected individuals generally were asymptomatic. In contrast to polycythemia vera, splenomegaly, leukocytosis, and thrombocytosis were not observed.
In one family a unique hemoglobin (Hb) abnormality, designated Hemoglobin Ypsilanti (Hb Ypsi), was associated with erythrocytosis. The starch gel and cellulose acetate electrophoretic patterns contained four abnormal hemoglobin components; two of these migrated cathodally to Hb A at pH 8.6 between Hb A and Hb F and comprised 15 and 25% of the total hemoglobin. The other two bands migrated between Hb F and Hb A2 and were minor components believed to be derived from Hb F and Hb A2. Pulmonary function studies are compatible with a shift of the oxyhemoglobin dissociation curve to the left. The primary structure abnormality of Hb Ypsi appears to have altered the manner of polymerization of the various types of hemoglobin polypeptide chains and to have increased the oxygen affinity.
The electrophoretic patterns of the hemoglobins of the other two families were normal, suggesting that not all inherited erythrocytosis is due to hemoglobinopathies. Hemoglobin electrophoresis should be routinely included in the investigation of erythrocytosis, especially when it is familial.