Hb F-SickKids (HBG2: C.308A > G): A Novel γ-Globin Variant Associated with Transient Neonatal Cyanosis.

We report a novel fetal hemoglobin variant, HBG2:c.308A > G [Gγ(102(G4)Asn > Ser], in a male neonate presenting with cyanosis and low oxygen saturation that resolved three months after birth, coinciding with the temporal decrease in the variant hemoglobin. Further molecular analysis confirmed maternal inheritance of this variant. The HBG2:c.308A > G variant parallels known low-oxygen-affinity mutations at the same position in the HBB and HBG2 genes, supporting its role in transient neonatal cyanosis. This variant has been designated Hb F-SickKids. Identifying such variants is important for timely diagnosis, avoiding unnecessary interventions, and facilitating accurate genetic counseling and reproductive planning.