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Pediatric Spinal Muscular Atrophy (SMA)

Spinal muscular atrophy (SMA) is a genetic disorder that affects how a person can control their muscle movements.

What is Pediatric Spinal Muscular Atrophy (SMA)?

Children with SMA have trouble controlling their muscle movement. This condition is caused by a loss of specialized nerve cells – called motor neurons – located throughout the spinal cord and in the part of the brain that is connected to the spinal cord (brainstem). That loss of motor neurons causes weakness and wasting (atrophy) of the muscles that children use for many activities, including crawling, walking, sitting up and controlling the head.

What are the different types of Pediatric Spinal Muscular Atrophy (SMA)?

Spinal muscular atrophy is split into four types:

Type I spinal muscular atrophy

Also called Werdnig-Hoffman disease, this type is severe and diagnosed at birth or within the first few months of a baby’s life. Babies with this condition are developmentally delayed and have breathing and swallowing problems.

Type II spinal muscular atrophy

This type of spinal muscular atrophy generally begins between 6 and 12 months of age. Babies with this condition can sit without support, but may need assistance getting to the seated position. Individuals with this condition cannot stand or walk without assistance.

Type III spinal muscular atrophy

Also called Kugelberg-Welander disease, this is a milder type that usually begins to appear during early childhood (birth to 5 years*) or adolescence (10 to 19 years**). Individuals with this condition can stand and walk without assistance, but, over time, walking and climbing stairs can become difficult.

Type IV spinal muscular atrophy

This type occurs after age 30 and usually only affects the muscles close to the center of the body (proximal muscles), such as the upper arms and legs.

*Age of early childhood as defined by the Centers for Disease Control (CDC).
**Age of adolescence as defined by the World Health Organization (WHO).

What are the signs and symptoms of Pediatric Spinal Muscular Atrophy (SMA)?

The signs and symptoms of spinal muscular atrophy vary according to the specific type an individual has. Possible symptoms include:

  • Breathing and swallowing problems
  • Difficulty sitting or reaching a seated position unassisted
  • Difficulty walking or climbing stairs
  • Inability to hold up the head
  • Muscle weakness
  • Tremors or twitching

How is Pediatric Spinal Muscular Atrophy (SMA) treated?

SPINRAZA (nusinersen) is a new drug that has been developed to treat some types of spinal muscular atrophy. 

Pediatric Spinal Muscular Atrophy (SMA) Doctors and Providers