The muscular dystrophies are a group of inherited disorders described by progressive muscle degeneration and weakness. Of the 9 muscular dystrophies, Duchenne muscular dystrophy (DMD) is the most common.
DMD is an X-linked recessive condition which presents in early childhood and inevitably progresses. DMD is caused by mutations in the dystrophin gene (located on the X-chromosome) which results in the absence of dystrophin, a structural protein that helps keep muscle cells intact.
It affects boys more frequently than girls, usually appearing between 3-5 years of age. Experts estimate that 1 out of 3600 boys are born with Duchenne’s.
Most patients have symptoms by age 3 years and may appear as early as infancy. DMD primarily presents itself in children with delays in motor milestones which include sitting and standing. Owing to progressive muscle weakness associated with loss of muscle mass, children may be seen with a strange waddling gait and increased difficulty in standing up or climbing stairs. The lower extremities are affected more severely than upper body though muscle weakness arises in arms and neck. Back and chest deformities may also be present as the muscles in the torso fail to hold the body in a correct position. Calf muscles initially enlarge and the enlarged muscle tissue is eventually replaced with fat and connective tissue (pseudohypertrophy).
There is a noticeable steady decline in muscle strength between the ages of 6 and 11 years. By then, braces may be required for walking and eventually will be confined to a wheelchair. Bones develop abnormally, causing skeletal deformities of the spine and other areas. This in turn leads to respiratory disorders. Cardiomyopathy occurs in almost all cases by the time the individual is in his teenage years. Intellectual impairment may occur.
Breathing complications and cardiomyopathy are common causes of death for patients affected with DMD.
The initial investigation for DMD is analysis of serum CK. High levels of CK indicate DMD. For a more accurate diagnosis a combination of Genetic analysis, muscle biopsy and detailed clinical observation of muscle strength and function is advocated.
Since mutations can be transmitted to the offspring only through the mother, prenatal tests can detect common mutations in the unborn child.
While there is no cure, several measures can be taken to improve the quality of life for the person with this disease. Treatment is generally aimed at controlling the onset of symptoms to maximize the quality of life. Physical therapy and remaining as active as possible are usually necessary to keep the muscles from deteriorating at a faster rate. Regular evaluations help doctors keep track of the heart and respiratory system as the child matures to treat issues as they arise. Bracing is often required to be able to walk. Wheelchairs enable mobility when they are no longer able to use braces.
Currently there is considerable ongoing research which includes exon-skipping, stem cell replacement therapy, analog up-regulation, gene replacement and supportive care to slow disease progression.
Recognizing the symptoms early on can help parents begin treatment as soon as possible. Early diagnosis is important so these treatments can begin promptly.
This article was contributed by Genpharm Services, a leading pharmaceutical marketing firm offering full market access services into the MENA region for specialty, rare disease, orphan drugs & biotech companies. To find out more about Genpharm click here.