MSTN and Duchenne muscular dystrophy: The results of our study are in line with a previous finding in DMD that higher Cr/Crn is related to lower motor performance measured by functional performance.15 Lower myostatin levels correlated weakly with decreased function in patients with DMD and limb-girdle muscular dystrophy type 2B.16 These results could be replicated in our BMD cohort when only taking baseline measurements into account for myostatin (ρ = −0.410, p = 0.052, data not shown), but not for Cr/Crn (ρ = 0.279, p = 0.177, data not shown).