Two different mutations in codon 97 of the beta-globin gene cause Hb Malmö in Sweden

An abnormal hemoglobin with increased oxygen affinity, Hb Malmö [alpha 2 beta 297(FG4)His-->Gln], was found to cause erythrocytosis in two apparently unrelated Swedish families. Direct nucleotide sequencing of amplified DNA demonstrated a CAC-->CAA substitution in one family and a CAC-->CAG substitution in the other. Both mutations resulted in a His-->Gln substitution in codon 97. This finding prompted us to examine the possible point mutations underlying the different hemoglobin variants reported in the literature.