Hb Youngstown [β101(G3)Glu → Ala; HBB: c.305A > C]: An unstable hemoglobin variant causing severe hemolytic anemia.

Hb Youngstown is a rare hemoglobin (Hb) variant caused by substitution of glutamic acid with alanine at amino acid residue 101 of the β-globin chain as a result of an A > C transversion on the β-globin gene nucleotide sequences [β101(G3)Glu → Ala; HBB: c.305A > C]. We now report three patients from two different families, one from South Africa and the other from Costa Rica, who are heterozygous for this Hb variant.