SMA is the #1 genetic killer of infants and young children. There is no treatment and there is no cure. SMA is degenerative and affects the muscles. The brain is never affected. Testing has shown that those with SMA have at least average to above average intelligence. 1 in 40 people unknowingly carry the recessive gene responsible for SMA. When both parents carry the SMA gene, there is a 1 in 4 chance that they could have a baby born with SMA. Few have any known family history. SMA does not discriminate based on race, ethnicity or gender.
SMA is classified into four categories, Type I, II, III and IV.
Type I SMA is usually diagnosed between 3 and 6 months of age. Mothers may later recall the baby not moving as much during the last month of pregnancy. They are not able to roll over, crawl, hold up their head, sit up without support or walk. All of their muscles are extremely weak and have very little movement especially in their legs, upper arms and neck. Some babies hands and wrists remain fisted and appear to face the wrong way. Their arms usually move only from the elbows down. The legs assume a frog-like position. The head may tilt to one side due to the lack of neck muscles. Their chest may appear concave or very skinny at the top, with a big belly shaped like a bell. Babies and children affected usually have expressive, bright faces and eyes. SMA affects all muscle systems as well as sucking, swallowing, digesting food and excretion. Common problems are constipation, controlling excessive drooling, and getting proper nutrition and calories for enough weight gain. A common cold can easily turn into pneumonia. Respiratory failure can occur when they no longer have the lung or chest muscles needed to allow them to breathe on their own. These are usually responsible for taking the lives of these children. Parents are faced with two major decisions for their SMA Type I child. The first is whether or not to put in a feeding tube, usually a G-tube which is surgically placed into the stomach. Doing this this helps to prevent pneumonia as well as provide nourishment when they have lost their ability to suck and swallow. The second decision is whether to place their children on a breathing machine or ventilator. This decision needs to made when the child goes into respiratory failure. The life expectancy for a baby that does not have a permanent ventilator is 8 months of age. 80% die by the age of 1 year and 90% die before the age of 2. The life expectancy varies when placed on a ventilator and can be longer based on the severity and progression of Type I SMA.
Type II SMA is usually diagnosed between 15 months and 2 years of age. These children are able to get themselves in a sitting position however they are not able to remain seated unassisted. Sometimes braces along with therapy allow the child to crawl. In some instances, children have been able to stand with braces but they will most often never be able to walk. Weakness will continue to increase over time. Feeding and swallowing are usually not affected but in some cases there can be problems. The life expantancy for SMA II widely varies. Some pass away at an early age while others can live into adulthood.
Type III SMA is usually diagnosed between 18 months and early adulthood. These children are able to stand and walk, however they have difficulty doing so. Weakness progresses over time and they will most likely become wheelchair bound. The life expectancy for SMA III is normal is most cases.
Type IV SMA is an Adult form of SMA. It is usually diagosed around 35 years of age. Weakness will get progressively worse. The life expectancy for SMA Type IV is normal.
SMA was selected by the National Institutes of Health (NIH) as the disease closest to treatment of more than 600 neurological disorders.