Learn About SMA What is SMA?

SMA is an inherited disease in which the children are not able to build muscle effectively.  The disease affects the motor neurons which allow the brain to communicate with the muscles and tell them to grow.  The children are born perfectly healthy but then begin to loose muscle tone, strength, and control.  The muscles closest to the trunk are affected first and most severely. This lack of muscle growth will most often affect crawling, walking, head control, as well as swallowing.  As the disease progresses it typically affects breathing, swallowing, and coughing.  Because of these facts the kids become more susceptible to illness.  In the most severe cases a common cold could literally be fatal.

Simply put, the line of communication between the brain and the muscles is slowed and eventually cut off. The brain however is unaffected by the disease.  SMA kids have normal intellectual activity while their bodies begin to fail them.


There are 4 general  Types of SMA

There are four typical groups of SMA which are generally categorized by when symptoms present themselves.

Type I, Acute Form of SMA (Werdnig-Hoffmann Disease): Diagnosis is typically between 0 and 6months.
Prognosis Type I - Only 50% live to see their first birthday and 90% die before their second birthday.

Type II, Intermediate Form of SMA: Diagnosis is typically between 6 and 18 months.
Prognosis Type II – Life expectancy ranges from early childhood to early adulthood.

Type III, Mild Form of SMA (Kugelberg-Welander or Juvenile Spinal Muscular Atrophy): Diagnosis is typically after 18 months.
Prognosis Type III – most afflicted live into adulthood and have a life expectancy that is close to normal.

Type IV, Adult Form of SMA: Diagnosis is typically after the age of 30.
Prognosis Type IV – Most afflicted have a normal life expectancy.

How is SMA diagnosed?

SMA can be diagnosed through a simple blood test that screens for the deletion of the gene known as Survival Motor Neuron, SMN1. 

For a slightly more genetic explanation please click here

To view an in depth genetic discription of SMA produced by Families of SMA please click here

Quick FactsAbout SMA

  • 1 in every 40 people, or nearly 10 million Americans, UNKNOWINGLY carries the gene responsible for SMA.  Few have any known family history.
  • SMA is a genetic recessive disease that kills more babies than ANY other inherited disease.  It is the number one genetic killer of children under the age of two.
  • 50% of SMA Type I babies don't live to see their 1st birthday.
  • 90% of SMA Type I babies don't live to see their 2nd birthday.
  • There is currently no treatment and no cure, but the National Institutes of Health (NIH) and the National Institute of Neurological Disorders and Stroke (NINDS) selected SMA as the disease closest to treatment of more than 600 neurological disorders.
  • Because scientists know so much about SMA, it is considered a "model" disease with direct impact on research into many other diseases potentially benefiting millions of people.
  • The American College of Medical Genetics recommends that SMA carrier testing be made available to ALL couples planning a family, regardless of ethnicity or family history.


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