Hemoglobinopathies Due to Abnormal Functional Properties of Hemoglobin Molecule Part II. Stable Abnormal Hemoglobins with Increased Oxygen Affinity, Frequently Causing Polycythemia
In the first part of this review article stable abnormal hemoglobins of high oxygen affinity causing erythrocytosis were dealt with. About a half of them are due to mutation in the α1β2contact region of hemoglobin molecule, and the remaining half are mutational products originating in α1β1 contact, heme contact, 2,3 DPG binding site, etc. In the present paper, which forms the second part, stable variants of high oxygen affinity with mutations in the carboxy terminal segment, which cause either erythrocytosis or not, and the stable high oxygen affinity variants, the mutation of which involve α1β2 contact without association of erythrocytosis are described. In addition, instances of stable hemoglobin variants of increased oxygen affinity which do not lead to overt clinical symptoms are also discussed.