Spinal Muscular Atrophy (SMA)

What is spinal muscular atrophy?

Spinal muscular atrophy (SMA) is a rare genetic condition in which muscles throughout the body are weakened because cells in the spinal cord and brainstem do not work properly. SMA is the number one genetic cause of infant mortality.

There are three types of SMA:

  • Type I is the most severe form of SMA. It’s sometimes called Werdnig-Hoffmann disease. Children with type I have limited movement, can’t sit without support, and have trouble breathing, feeding and swallowing. Symptoms begin within months after birth. Many children with type I do not live past age 2.
  • Type II is an intermediate form of SMA. Children with this type may sit without support at some point but cannot walk on their own. Symptoms typically start between 6 and 18 months of age. Depending on the severity of symptoms, children with type II may have a normal life span. 
  • Type III is a milder form of SMA. It’s also known as Kugelberg-Welander disease and resembles muscular dystrophy. While children with type III usually are able to walk, most have some difficulty walking. Some may eventually need to use a wheelchair. Symptoms usually appear around 18 months of age or in early childhood. Children with this type of SMA generally have an almost normal life expectancy. 

A new treatment for SMA, called nusinersen (brand name Spinraza), offers new hope for children and adults with this condition. Before this medication became available, treatment of SMA consisted of managing the symptoms, providing respiratory support as needed and preventing disease complications.

How we care for spinal muscular atrophy

The Spinal Muscular Atrophy Program at Boston Children’s Hospital brings together a team of experts from different specialties experienced in caring for children with SMA. We hold a dedicated SMA clinic once a month so that your child can receive all of their SMA-related care in a single visit. This approach means that our various specialists can all work closely with your family to make sure your child’s care is well coordinated.

Our program offers nusinersen for treatment of SMA and has been involved in clinical trials of nusinersen since 2011.

Gene therapy for SMA

Boston Children's is helping to lead a gene therapy trial for SMA. The trial — which delivers a working copy of the SMN1 gene to motor neurons in SMA patients — may be a promising new approach to treating the condition. Learn more about our Gene Therapy Program