Spinal Muscular Atrophy (SMA) attacks what are known as the anterior horn cells in the spinal cord, causing the disease to affect the voluntary muscles needed for things like crawling, walking, head and neck control, and swallowing. SMA is the number one genetic killer of children under age 2, and one out of every 40 people carries the SMA gene.
SMA is considered an autosomal recessive disease – both parents must have the gene.Types of Spinal Muscular Atrophy
Type I Acute (Severe): Also called Werdnig-Hoffmann Disease, Type I SMA is diagnosed in children usually within the first six months after birth. Children with Type I are unable to lift their head or reach normal physical milestones. They may also have trouble swallowing, and breathing is often labored. Most children with Type I SMA do not reach age two.
Type II (Chronic): Most cases of Type II SMA are diagnosed by the time a child reaches age two. Children with this form of SMA may be able to sit on their own, but they need help sitting up. They also may be able to stand up and even walk, but often need the help of bracing. Type II SMA usually does not cause a person to have trouble swallowing or breathing. Some children with SMA may survive into adulthood, but others often suffer breathing problems and illnesses because of to weakened chest and respiratory muscles.
Type III (Mild): Type III SMA is often called Kugelberg-Welander or Juvenile Spinal Muscular Atrophy. It is diagnosed after a child has reached 18 months. Sometimes a child has reached teenage years before Type III SMA is discovered. Symptoms of Type III can be difficulty walking or standing up.
Type IV (Adult Onset): Adult Onset SMA is diagnosed after age 35 and is characterized by a very slow progression.
Adult Onset X-Linked SMA: This type of SMA is also called Kennedy's Syndrome or Bulbo-Spinal Muscular Atrophy and only afflicts men.
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