ACTN3 and Duchenne muscular dystrophy: Among these, SPP1 and LTBP4 are validated genetic modifiers linked to LoA in steroid-treated boys (Flanigan et al., 2013; Bello et al., 2015; van den Bergen et al., 2015), while promising new biomarkers, as ACTN3 and CD40, or THBS1 as locus modifier, were recently identified as associated with LoA in DMD boys (Bello et al., 2016; Hogarth et al., 2017; Weiss et al., 2018).