• duchenne muscular dystrophy o onset 3 to 5 yrs o clinical § weakness o distribution § proximal > distal § symmetric § legs & arms § most involved muscles: adductor magnus in legs § relatively spared muscles: gracilis & sartorius o course § reduced motor function by 2 to 3 years § steady decline in strength: after 6 to 11 years o gowers sign: standing up with the aid of hands pushing on knees ...