What you need to know about spinal muscular atrophy (SMA)

What is SMA?

SMA is a severe neuromuscular disease caused by a genetic defect in the SMN1 (survival motor neuron 1) gene. It leads to the loss of motor neurons and results in progressive muscle weakness and paralysis.


It's the number 1
genetic cause of infant death


As many as 1 in 10,000
live births will be affected


1 in 50 americans
are genetic carriers


SMA can affect people
of any race or gender


Survivors REQUIRE lifelong
care and support

Be SMA aware

SMA is a rare condition, yet it is the number one genetic cause of infant death. Early diagnosis is critical in this fast-moving disease.

Signs and Symptoms of SMA
Watch this video to hear parents of children with SMA talk about the early signs and symptoms to look for to help reach a diagnosis quickly.

There are four types of SMA:

Type 1 (also called werdnig-hoffman disease) is the most severe

Early onset with diagnosis usually in an infant's first 6 months

Most severe type with 90% mortality or need for permanent ventilation support by 2 years old

60% of all sma cases are type 1

Type 1 symptoms:

  • Hypotonia or "floppy baby syndrome" is an abnormal limpness in the neck and limbs
  • Muscle weakness (particularly in the legs)
  • Poor head control
  • Abdominal breathing, also called "diaphragmatic" or "belly breathing," is contraction of the diaphragm rather than the chest, when breathing
  • Bulbar muscle weakness which is exhibited by a weak cry, difficulty swallowing and aspiration
  • Inability to sit unsupported

Type 2 (also called Dubowitz Syndrome)

  • Onset between 6 to 18 months of age
  • Reduced life expectancy; 68% alive at age 25
  • Will never be able to walk without support
  • Most will never stand without support

Type 3 (also called Kugelberg-Welander disease or juvenile SMA)

  • Onset after 18 months
  • Can be diagnosed as late as the teenage years
  • Individuals affected are initially able to walk but have increasingly limited mobility as they grow

Type 4 (Adult Onset)

  • Very rare
  • Symptoms can start as early as 18 years but usually begin after age 30
  • Mobility characteristics are similar to Type 3