Hb Nebraska [β86(F2)Ala→Ile (HBB:c.259G>A;260C>T)]: a unique high oxygen affinity hemoglobin variant with a double nucleotide substitution within the same codon.

A new high oxygen affinity hemoglobin (Hb) variant, Hb Nebraska [β86(F2)Ala→Ile, GCC>ATC; HGVS: HBB: c.259G>A;260C>T] is reported. This variant was not identified by routine methods and was only suspected due to erythrocytosis and an abnormal p50 value. The variant was analyzed by DNA sequencing and mass spectrometry (MS). The β chain variant is unusual in that it has two nucleotide substitutions occurring at the same codon.