Juvenile form spinal muscular dystrophy, Type III

**Definition:** In SMA type 3, weakness of muscles is seen after 18 months of age. The child is able to sit and stand independently. There is a limb girdle-type of distribution of weakness causing waddling gait, falls, and difficulty with running. The ability to walk may be lost, requiring a wheelchair as the disease progresses. The life expectancy may be normal.