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Articles » NINDS Spinal Muscular Atrophy Information Page: NINDS

NINDS Spinal Muscular Atrophy Information Page: NINDS

Article title: NINDS Spinal Muscular Atrophy Information Page: NINDS

Main condition: Spinal muscular atrophy

Conditions: Spinal muscular atrophy

What is Spinal Muscular Atrophy?
Spinal muscular atrophy (SMA) is a genetic, motor neuron disease characterized by wasting of the skeletal muscles caused by progressive degeneration of the anterior horn cells of the spinal cord. The disorder causes weakness and atrophy of the voluntary muscles. Weakness is often more severe in the legs than in the arms. There are many types of SMA; some of the more common types are described below.

SMA type I, also called Werdnig-Hoffmann disease, is evident in utero or within the first few months of life. There may be a paucity of fetal movement in the final months of pregnancy. Symptoms may include hypotonia (floppiness of the limbs and trunk), diminished limb movements, swallowing and feeding difficulties, and impaired breathing. Affected children never sit or stand and usually die before the age of 2.

Symptoms of SMA type II usually begin between 3 and 15 months of age. Features may include inability to stand or walk, respiratory problems, hypotonia, decreased or absent deep tendon reflexes, and muscle fasciculations (involuntary contractions of small bundle muscle, evident as twitching of limb or tongue muscles). These children may learn to sit but do not stand. Life expectancy varies.

Symptoms of SMA type III (Kugelberg-Welander disease) appear between 2 and 17 years of age, and include abnormal gait; difficulty running, climbing steps, or rising from a chair; and a fine tremor of the fingers.

The childhood SMAs are all autosomal recessive diseases. This means that they are familial and more than one case is likely to occur in the same generation of a family - in siblings or cousins. The parents are usually asymptomatic but carry the gene. Cousin marriages are more common in these families than in others. If one case has occurred in a family, antenatal diagnosis can be made in a subsequent pregnancy. The gene and gene product have been identified providing accurate diagnostic tests.

Kennedy syndrome or progressive spinobulbar muscular atrophy may occur between 15 and 60 years of age. Features of this type may include weakness of the facial and tongue muscles, dysphagia (difficulty swallowing), dysarthria (speech impairment), and gynecomastia (excessive development of male mammary glands). The course of the disorder varies but is generally slowly progressive. Kennedy syndrome is an X-linked recessive disorder, which means that it occurs only in men. Women carry the gene. A diagnostic DNA test is available.

Congenital SMA with arthrogryposis (persistent contracture of joints with fixed abnormal posture of the limb) is a rare disorder. Manifestations include severe contractures, scoliosis (curvature of the spine), chest deformity, respiratory problems, micrognathia (unusually small jaws), and ptosis (drooping of upper eyelids). Adult SMA may begin between 40 and 60 years of age and progresses rapidly, with an average life expectancy of about 5 years. Most cases prove to be variants of amyotrophic lateral sclerosis. Symptoms include progressive limb weakness and atrophy of the muscles, difficulty speaking and swallowing, and respiratory problems.

Is there any treatment?
Treatment of all forms of SMA is symptomatic and supportive and includes treating pneumonia, scoliosis, and respiratory infections, if present. Also, physical therapy, orthotic supports, and rehabilitation are useful. Genetic counseling is imperative.

What is the prognosis?
The prognosis for individuals with SMA varies depending on the type of SMA and the degree of respiratory function. Some may appear to be stable for protracted periods, but improvement is not to be expected.

What research is being done?
The NINDS supports research on the genetic etiology of SMA. The goals of this research are to characterize the genes and gene products, to study gene function and disease pathophysiology, and to find ways to prevent, treat, and, ultimately, cure these diseases. There has been great progress in the last decade and the rate of research progress is accelerating.


Andrew's Buddies [For Research on Spinal Muscular Atrophy]
P.O. Box 785
Richmond, VA 23218-0785
Tel: 804-698-8839
Fax: 804-698-8802

Families of Spinal Muscular Atrophy
P.O. Box 196
Libertyville, IL 60048-0196
Tel: 847-367-7620 800-886-1762
Fax: 847-357-7623

March of Dimes Birth Defects Foundation
1275 Mamaroneck Avenue
White Plains, NY 10605
Tel: 914-428-7100 888-MODIMES (663-4637)
Fax: 914-428-8203

Muscular Dystrophy Association
3300 East Sunrise Drive
Tucson, AZ 85718-3208
Tel: 520-529-2000 800-572-1717
Fax: 520-529-5300

This fact sheet is in the public domain. You may copy it.Provided by:
The National Institute of Neurological Disorders and Stroke
National Institutes of Health
Bethesda, MD 20892


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