Erythrocytosis secondary to increased oxygen affinity of a mutant hemoglobin, hemoglobin Kempsey.

\TO CLASSES of amino acid substitutions in hemoglobins have profound effects on the major function of this protein, oxygen transport. The first includes the hemoglobins M’ and hemoglobin Kansas,2 which result in cyanoSis in heterozygous subjects and no significant erythrocytosis. The second class, represented by hemoglobin Chesapeake3 and hemoglobin Yakima,4 is assocated with erythrocytosis in the heterozygote. This report describes a third family in which members heterozygous for an abnormal hemoglobin, termed hemoglobin Kempsey, have erythrocytosis. Features shared by hemoglobins Chesapeake, Yakima and Kempsey include an increased oxygen affinity and a common structural region affected by the amino acid substitution, suggesting that the altered function in all three may have a similar structural explanation.