This observation was validated in some independent DMD cohorts (Bello et al., 2012; Bello et al., 2015; Chen et al., 2020), but not in others (Flanigan et al., 2013; Van Den Bergen et al., 2015), possibly due to a role of osteopontin in the modification of response to glucocorticoid treatment, rather than DMD severity per se; a phenomenon that was also investigated in vitro (Barfield et al., 2014; Vianello et al., 2017). Here, SPP1 is linked to Duchenne muscular dystrophy.