Spinal Muscular Atrophy (SMA)

Spinal muscular atrophy (SMA) is a genetic disease affecting the central nervous system, peripheral nervous system, and voluntary muscle movement. SMA is a debilitating neuromuscular condition that causes individuals to slowly lose the ability to walk, eat and breathe.

Types of SMA

  • Type 1: (Werdnig-Hoffmann SMA): Also called infantile-onset SMA. A child with this type often has symptoms just after birth. An infant may have trouble moving, swallowing and feeding. The infant may not be able to hold up their head.
  • Type 2: (Juvenile or chronic SMA): A child with this type is often diagnosed at age 6 to 18 months. The main symptom is muscle weakness all over the body. This causes trouble walking and standing. Children with type 2 may need help moving around. They may need a walker or wheelchair. They often live into adulthood, but they are more prone to respiratory infections.
  • Type 3 (sometimes called Kugelberg-Welander disease): This is the mildest form of SMA. It can affect children from 18 months old up to their teen years. The most common symptoms include clumsiness, trouble walking and climbing steps, fine tremor, and muscle weakness. Children with type 3 often have trouble getting up from a sitting position.
  • Type 4: This is characterized as a mild disease and found in less than five percent of cases. Age of onset is not clearly defined although some experts suggest onset occurs in the third decade of life. Persons with type 4 reach all major motor milestones and have a normal lifespan.