MYH6 and Duchenne muscular dystrophy: This is accompanied by a robust regenerative response initially in DMD: for example, the proportion of regenerating fibres expressing developmental MyHC isoforms varied from 38 to 47% in quadriceps biopsies from four DMD patients aged 4–13 years (55), 24–33% in muscle biopsies from five DMD patients aged 4.3–8.2 years (20) and a mean of 32% in muscle biopsies from three DMD patients aged 3.3–6.8 years (56).