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Spinal Muscular Atrophy

Spinal Muscular Atrophy (SMA) is a genetic neuromuscular disorder for which there is no cure. It is a result of a missing or mutated gene and affects the voluntary muscles throughout the body. This disease affects 1 in 6000 babies born and about 1 in 40 people are genetic carriers. It is one of the most prevalent genetic disorders and can affect individuals of any age, race or gender.

Individuals with SMA have difficulty with activities such as crawling, walking, head and neck control, and swallowing. They have weakness in limbs, with legs generally more affected than arms, and difficulty feeding and swallowing. Patients also have an increased risk of developing pneumonia and other lung problems due to involvement of respiratory muscles. Sensation is not affected and intellectual activity is normal.

SMA is an autosomal recessive genetic disease. This means than in order for a child to be affected, both parents must be carriers of the abnormal gene and both must pass this gene onto their child. If both parents are carriers, there is a 25% chance of the child inheriting the disease.

The missing or mutated gene is SMA is called survival motor neuron 1 (SMN1), which produces a protein called Survival Motor Neuron (SMN) protein. This protein is critical to the survival and health of motor neurons, which are nerve cells in the spinal cord that send out nerve fibers to muscles throughout the body. Without SMN, nerve cells atrophy and eventually die, resulting in muscle weakness.

There are four types of SMA and patients are classified into each type based on the physical milestones achieved at the onset of the disease. Type I and II are the most prevalent.

• SMA Type I
  Type I, or Werdnig-Hoffmann Disease, is the most severe form of SMA. It strikes infants between birth and six months old. Children affected with Type I cannot sit without support. SMA Type I can progress very rapidly, leading to early childhood death.
• SMA Type II
  Type II affects infants between seven and 18 months old. Patients may be able to sit unaided or even stand with support. They are at increased risk for complications from respiratory infections. SMA Type II usually progresses slowly and survival into adulthood is common.
• SMA Type III
  Type III, also known as Kugelberg-Welander Disease, is the least deadly form of childhood-onset SMA. It strikes children as early as the age of 18 months, but can surface as late as adolescence. Type III patients are able to walk, but weakness is prevalent. Most patients eventually need to use a wheelchair.SMA Type III progresses slowly and life span is usually not affected.
• SMA Type IV
  Type IV is the adult form of the disease. Symptoms tend to begin after age 35 and muscles used for swallowing and respiratory function are rarely affected. SMA Type IV has very slow progression and life span is usually not affected.

Typically, patients with SMA have continued lose of motor function over time. SMA does not affect sensation and intellectual activity in patients.

California Stem Cell has completed efficacy studies for SMA stem cell replacement therapy. Discussions with the FDA and pivotal pre-clinical safety studies are under way.

SMA Support