Hb Alcorn County: A β-Globin Variant [β40(C6)Arg→Thr; HBB: c.122G>C (p.Arg41Thr)] with Increased Oxygen Affinity

We describe Hb Alcorn County, a heterozygous hemoglobin (Hb) variant, in a 6-month-old Hispanic male and his mother. DNA sequencing demonstrated a mutation on the HBB gene [β40(C6)Arg→Thr; HBB: c.122G>C (p.Arg41Thr)], predictive of a substitution of arginine to threonine at position 40 of the β-globin protein. This amino acid substitution involves the α1β2 contact and occurs at the same position as Hb Austin [β40(C6)Arg→Ser; HBB: c.[123G>C or 123G>T] (p.Arg41Ser)] and Hb Athens-GA [β40(C6)Arg→Lys; HBB: c.122G>A (p.Arg41Lys)], both of which show increased oxygen affinity.