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Spinal muscular atrophy   

Overview | Symptoms | Treatment | Prevention

Alternative names:

Werdnig-Hoffmann disease

Definition:

Spinal muscular atrophy is a group of inherited diseases that result in progressive muscle degeneration and weakness.

Causes and Risks

Spinal muscular atrophy is the second leading cause of neuromuscular disease. (Duchenne muscular dystrophy is number one.) Spinal muscular atrophy is inherited as an autosomal recessive trait and has an incidence of approximately 4 per 100,000 people.

In its most severe form (SMA I), infants are born floppy with weak, thin muscles, and feeding and breathing problems. Their lifespan seldom exceeds more than 2 to 3 years. Infants with SMA type II have less severe symptoms during early infancy, but they become progressively weaker with time. Survival time with type II is longer. SMA type III is the mildest form of the disease and symptoms may not appear until the second year of life. Often, weakness is first noted in the shoulder muscles and proximal leg muscles. Weakness is progressive and will eventually become profound, but children may survive into early adulthood.

Rarely, SMA may present in adulthood and is usually a milder form of the disease. It may be inherited in an autosomal dominant or autosomal recessive manner.

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