GSTM1 and Schnyder corneal dystrophy: In β-globinopathies, it can usually be predicted that in carrier couples with β0, severe β+, δβ variants, δβ-Lepore, and HbS, as well as co-inheritance of HbC, HbΕ, and Hb O-Arab with β0 and severe β+ variants, there is a 25% chance that their child will be affected by transfusion-dependent thalassemia (TDT) or sickle cell disease (SCD).