A Novel Hemoglobin Variant Associated with Congenital Erythrocytosis: Hb Seoul [β86(F2)Ala→Thr] (HBB:c.259G>A).

We report the identification of a novel hemoglobin (Hb) variant [β86(F2)Ala→Thr; HBB: c.259G>A], Hb Seoul, causing congenital erythrocytosis due to high oxygen affinity. The patient was a 33-year-old Korean man with isolated erythrocytosis. JAK2 somatic mutations were negative. Direct sequencing analyses revealed that the patient was heterozygous for c.259G>A, while other known causative genes (BPGM, EGLN1, EPAS, EPOR and VHL) had no mutation. β86(F2) is a critical residue that affects the oxygen affinity. The novel variant in our patient, Hb Seoul, adds to the previously reported 4 other Hb variants from β86(F2) substitutions that cause congenital erythrocytosis.