Structural and clinical characterization of Hb Móstoles (HBA2:c.176A>G; p.His59Arg): a new unstable alpha-globin variant with thalassemic features.

We report a novel α-globin gene variant, hemoglobin (Hb) Móstoles, characterized by a single nucleotide substitution in the HBA2 gene [α2 58(E7) His > Arg; HBA2:c.176A>G], associated with a 3.7-kb deletion in the homologous chromosome. This variant was identified in a Moroccan family living in Spain. The proband, a four-year-old girl, presented with microcytosis and hypochromia. The abnormal Hb was maternally inherited and detected in two of the proband's four siblings, while the 3.7-kb deletion was paternally inherited. Hb analysis using high-performance liquid chromatography and capillary electrophoresis revealed an abnormal peak in the Hb S region, with a concentration of approximately 3%. Hematological parameter assessment of the four carriers demonstrated that, despite being a structural hemoglobinopathy, Hb Móstoles is associated with an alpha-thalassemia phenotype and may exacerbate clinical manifestations when coexisting with other HBA1 and HBA2 mutations.