Understanding SMA
THE DISEASE
Spinal muscular atrophy (SMA), the number one genetic killer of
children under the age of two, is a group of inherited and often fatal
diseases that destroys the nerves controlling voluntary muscle movement,
which affects crawling, walking, head and neck control, and even
swallowing.
WHO IS AFFECTED?
- SMA is one of the most prevalent genetic disorders.
- One in every 6,000 babies is born with SMA. Of children diagnosed before age two, 50 percent will die before their second birthday.
- SMA can strike anyone of any age, race or gender.
- One in every 40 people carries the gene that causes SMA. The child of two carriers has a one in four chance of developing SMA.
THE TYPES OF SMA
- Type 1, or Werdnig-Hoffmann Disease, is the most severe form of SMA. Children with Type I tend to be weak and lack motor development, rendering movement difficult. Children afflicted with Type I cannot sit unaided and have trouble breathing, sucking and swallowing. Type I SMA strikes infants between birth and six months.
- Type II is slightly less severe. Type II patients may be able to sit unaided or even stand with support and usually do not suffer from feeding and swallowing difficulties. However, they are at increased risk for complications from respiratory infections.
Type II SMA affects infants between seven and 18 months old. - Type III, also known as Kugelberg-Welander Disease, is the least deadly form of childhood-onset SMA. Type III patients are able to stand, but weakness is prevalent and tends to eventually sentence its victims to a wheelchair. Type III SMA strikes children after the age of 18 months, but can surface even in adulthood.
- Type IV is the adult form of the disease in which symptoms tend to begin after age 35. Symptoms usually begin in the hands, feet and tongue, and spread to other areas of the body.
- Adult Onset X-Linked SMA, also known as Kennedy's Syndrome or Bulbo-Spinal Muscular Atrophy, occurs only in men.
Facial and tongue muscles are noticeably affected. In addition, these men also often have breast enlargement known as gynecomastia. Like all forms of SMA, the course of the disease is variable, but in general tends to progress slowly.
SMA does not affect sensation and intellectual activity in patients.
It commonly is observed that patients with SMA are unusually bright and sociable.
RESEARCH
- In 1999, investigators at The Ohio State University replicated SMA in a mouse model. The researchers have demonstrated that when the mice have high amounts of the SMN2 gene, which is present in all human SMA patients, the SMA phenotype is corrected and they develop normally. These findings support the conclusion that large amounts of the protein could act to prevent the damage caused by SMA or even reverse the impact of the disease.
- Since then, many more important research steps have been made. For details, please see SMA Research.
- This research was funded in large part by the volunteer driven, not-for-profit organization Families of SMA - http://www.fsma.org
TESTING
Prenatal counseling is available to couples who are carriers of SMA or who have lost a child to SMA. For details, please see SMA Genetics.
MORE INFORMATION
For more detailed information about SMA, please see Understanding SMA and SMA Information and Resources, and also our printable SMA Information flyer.
All the above information is from the FSMA Site