Duchenne Muscular Dystrophy (DMD)

• DMD (one of nine types) is a disorder of voluntary muscles with onset in early childhood and weakness and muscle atrophy, eventually including the heart and breathing muscles, causing death by early adulthood.
  
  

Myotonic Muscular Dystrophy (MMD)

• MMD has a severe life-threatening infancy-onset form and a milder adult-onset form characterized by difficulty relaxing muscles of the hands and progressive weakness in the face, arms and lower legs.
  
  

Spinal Muscular Atrophy (SMA)

• SMA symptoms range from severe with infancy-onset to mild with adult-onset. Motor nerves degenerate, causing muscular atrophy. Infants are weak and limp with difficulty sucking and crying.
  
  

Hereditary Motor-Sensory Neuropathy, Type I (HMSN-I)

• HMSN-I (most common of seven types) causes loss of the nerve's myelin sheath and slowed conduction of both motor and sensory nerves with onset by age 10 and poor balance, circulatory impairment of lower legs, muscle weakness, hammer toes and high arch.
  
  

Infantile-Onset Ascending Hereditary Spastic Paralysis (IAHSP)

• IAHSP causes damage to motor nerves with spastic paralysis beginning in the feet and legs and ascending to other muscles with onset at about 2 years and increasing weakness and inability to walk, talk and swallow by adolescence.