Hemoglobin Beth Israel: A Mutant Causing Clinically Apparent Cyanosis

We found that an abnormal hemoglobin with a very low oxygen affinity was responsible for overt cyanosis in an otherwise healthy adolescent. Hemoglobin Beth Israel, in which serine replaces the asparagine residue normally present at position 102 (G4) of the βpolypeptide chain, was associated with normal blood counts and no apparent exercise intolerance in the heterozygous carrier. Cyanosis resulted from a drastically right-shifted oxygen dissociation curve, whose position and shape could account for the absence of “physiologic” anemia. The whole-blood oxygen tension at 50 per cent oxygen saturation was 88 mm Hg (normally 26 ± 1 mm Hg), and the arterial blood was only 63 per cent saturated with oxygen despite a normal oxygen tension of 97 mm Hg. The hemolysate showed a low oxygen affinity but normal Bohr effect. Unexplained cyanosis, particularly in association with normal arterial oxygen tension should prompt a search for an abnormal hemoglobin, which may obviate the need for invasive diagnostic procedures. (N Engl J Med 295:125-130, 1976). I.N. the last 10 years, a number of human hemoglobin mutants have been described whose main functional abnormality is an abnormal affinity for oxygen. The majority of these (over 20 examples at present) showed a high oxygen affinity, and the usual presenting finding of the carriers was erythrocytosis. A smaller group of mutants were found to exhibit a low oxygen affinity, but with many of them, hemoglobin instability was a prominent finding, resulting in the clinical picture of a congenital Heinz-body hemolytic anemia.^{1 2}Only four reported mutants have been characterized primarily by their low oxygen affinities: hemoglobin Kansas,³hemoglobin Yoshizuka.