Spinal Muscular Atrophy (SMA) Types I, II, and III belong to a group of hereditary diseases that cause weakness and wasting of the voluntary muscles in the arms and legs of infants and children. The disorders are caused by an abnormal or missing gene known as the survival motor neuron gene 1 (SMN1), which is responsible for the production of a protein essential to motor neurons. Without this protein, lower motor neurons in the spinal cord degenerate and die. The type of SMA (I, II, or III) is determined by the age of onset and the severity of symptoms. Type I (also known as Werdnig-Hoffman disease, or infantile-onset SMA) is evident at birth or within the first few months. Symptoms include floppy limbs and trunk, feeble movements of the arms and legs, swallowing and feeding difficulties, and impaired breathing. Type II (the intermediate form) usually begins 6 and 18 months of age. Legs tend to be more impaired than arms. Children with Type II may able to sit and some may be able to stand or walk with help. Symptoms of Type III (also called Kugelberg-Welander disease) appear between 2 and 17 years of age and include difficulty running, climbing steps, or rising from a chair. The lower extremities are most often affected. Complications include scoliosis and chronic shortening of muscles or tendons around joints.
There is no cure for SMA. Treatment consists of managing the symptoms and preventing complications.
The prognosis is poor for babies with SMA Type I. Most die within the first two years. For children with SMA Type II, the
prognosis for life expectancy or for independent standing or walking roughly correlates with how old they are when they first
begin to experience symptoms - older children tend to have less severe symptoms Life expectancy is reduced but some individuals
live into adolescence or young adulthood. Individuals with SMA type III may be prone to respiratory infections but with care
may have a normal lifespan.
Between 2003 and 2012, the NINDS piloted the Spinal Muscular Atrophy Project to expedite therapeutics development for this
hereditary neurodegenerative disease. The Project was designed to accelerate the research process by identifying drugs that
increase the level of SMN protein in cultured cells, so that they could be used as potential leads for further drug discovery
and clinical testing. Read more about the history of this pioneering effort and how it led to collaboration with several pharmaceutical
and biotechnology companies. (LINK TO SUMMARY)
Fight SMA 1680 Duke Street Fourth Floor Alexandria, VA 22134 heatherlennon@fightsma.com http://www.fightsma.org Tel: 703-647-5032 |
Families of Spinal Muscular Atrophy 925 Busse Road Elk Grove Village, IL 60007 info@fsma.org http://www.curesma.org Tel: 800-886-1762 Fax: 847-367-7623 |
Spinal Muscular Atrophy Foundation 888 Seventh Avenue Suite 400 New York, NY 10019 info@smafoundation.org http://www.smafoundation.org Tel: 877-FUND-SMA (877-386-3762) 646-253-7100 Fax: 212-247-3079 |
Muscular Dystrophy Association 3300 East Sunrise Drive Tucson, AZ 85718-3208 mda@mdausa.org http://www.mda.org Tel: 520-529-2000 800-572-1717 Fax: 520-529-5300 |
Prepared by:
Office of Communications and Public Liaison
National Institute of Neurological Disorders and Stroke
National Institutes of Health
Bethesda, MD 20892
NINDS health-related material is provided for information purposes only and does not necessarily represent endorsement by or an official position of the National Institute of Neurological Disorders and Stroke or any other Federal agency. Advice on the treatment or care of an individual patient should be obtained through consultation with a physician who has examined that patient or is familiar with that patient's medical history.
All NINDS-prepared information is in the public domain and may be freely copied. Credit to the NINDS or the NIH is appreciated.
Last updated December 11, 2012