Spinal Muscular Atrophy

Cyril MIller
Per.6

Spinal Muscular Atrophy

Spinal muscular atrophy is a group of inherited diseases that cause muscle damage and weakness, which get worse over time and eventually lead to death.

Causes:
Spinal muscular atrophy (SMA) is a collection of different muscle diseases. Grouped together, it is the second leading cause of hereditary neuromuscular disease, after Duchenne muscular dystrophy.
Most of the time, a person must get the defective gene from both parents to be affected. About 4 out of every 100,000 people have the condition.
The most severe form is SMA type I, also called Werdnig-Hoffman disease. Infants with SMA type II have less severe symptoms during early infancy, but they become weaker with time. SMA type III is the least severe form of the disease.
Rarely, SMA may begin in adulthood. This is usually a milder form of the disease.
A family history of spinal muscular atrophy is a risk factor for all types of the disorder.

Signs and Symptoms:
Signs:
Legs tend to weaken before arms. Hands may weaken eventually, but they usually stay strongest the longest, and, even if they do weaken, they usually remain strong enough for typing on a computer keyboard and other basic functions of modern life.In SMA types 1 through 4, the muscles closer to the center of the body (proximal muscles) usually are more affected, or at least affected much sooner, than the muscles farther away from the center. For example, the muscles of the thighs are weaker than the muscles of the lower legs and feet.

Symptoms:
Infants with SMA type I are born with very little muscle tone, weak muscles, and feeding and breathing problems.
With SMA type II, symptoms may not appear until age 6 months to 2 years.
Type III SMA is a milder disease that starts in childhood or adolescence and slowly gets worse.
Type IV is even milder, with weakness starting in adulthood.
Often, weakness is first felt in the shoulder and leg muscles. Weakness gets worse over time and eventually becomes severe.
Symptoms in an infant:
Breathing difficulty, leading to a lack of oxygen
Feeding difficulty (food may go into the windpipe instead of the stomach)
Floppy infant (poor muscle tone)
Lack of head control Diagnosis:
The doctor may order a blood test for an enzyme called creatine kinase (CK), an enzyme that leaks out of muscles that are deteriorating. This is a nonspecific test because CK levels are elevated in many neuromuscular diseases.
Treatmeant:
Medications such as valproic acid, phenylbutyrate, hydroxyurea, and albuterol have been shown to increase SMN transcription in laboratory studies.Surgical revision may provide stable correction of the spine, and early orthopedic intervention may be indicated in patients in whom prolonged survival is anticipated. Ensuring optimal caloric intake enables patients to use weak muscles to their maximum capacity without incurring obesity as a comorbid condition.