Information for doctors

Duchenne Muscular Dystrophy (DMD) is a relatively common and severe neuromuscular disorder, affecting approximately one in every 3,000-4,000 male live births.

Genetic aspects:

DMD is a genetic condition inherited as an x-linked trait. Often there are no other members of the family affected. This is usually the result of a de-novo genetic event that has occurred in the affected child; or that the mother, if she is a carrier of the genetic defect, usually does not manifest any sign of the disease (because of the x-linked inheritance). The gene responsible for DMD is known and mutations can be relatively easily found in approximately two thirds of affected children. Prenatal diagnosis and carrier detection is available through the Clinical Genetic Centres.

Clinical features:

The hallmark of the disease is the progressive weakness of all muscles; proximal muscles of the limbs are most severely affected. Children usually present with mild delay of the motor milestones such as walking and with tip-toe and unsteady gait. Difficulties rising from the floor, going upstairs and running are usually evident in the first two to three years of life. Enlarged calf muscles can be seen in most children especially in the early phases of the disease. A frequently associated feature (30% of cases) is mild mental retardation. The presentation with predominantly “cognitive” problems is not uncommon (speech delay, for example). This is not progressive.

The weakness, however, is progressive and children with DMD will lose ambulation by the age of thirteen years; the mean age being approximately nine years. This is due to a combination of weakness and contractures affecting the ankles, knees and hips.

Affected children confined to a wheelchair are at high risk of developing spinal curvatures; more than 90% will eventually develop a significant scoliosis. Appropriate management (bracing) reduces the rate and very often spinal surgery is required to stop the progression of the scoliosis.

Respiratory muscles are also affected and this becomes a clinical problem usually in the late teens; respiratory failure causing night time hypoventilation is common at this age and is often followed by death after a few months if not treated (with night time ventilatory support using facial or nasal mask and BiPap machines). Cardiac muscle is also affected; however, because of the immobility, patients with DMD rarely develop signs of cardiac failure.

Diagnosis

The diagnosis is performed in centres where there is expertise to deal with these conditions but serum creatine kinase is a very useful initial screening test. If the CK is normal, the diagnosis of DMD is excluded, as affected children invariably have serum levels more that ten times normal.

A muscle biopsy (preferably with a needle) is often taken to confirm the diagnosis and a genetic test will also help in establishing the diagnosis and in providing genetic counseling to the family.

Treatment

There is no definitive cure available yet for this condition.

Steroids do have a mild beneficial effect in slowing the disease process and individual children may benefit from these drugs.

Management

One essential aspect of the management of this disease is the regular stretching of joints. This is usually done on a daily basis by parents; supported by regular physiotherapy/hydrotherapy sessions, with supervision by one specialist physiotherapist and a tertiary referral centre with expertise in the condition.

Prolongation of ambulation using long-leg or ischial-bearing callipers is an effective way to slow the progression of the scoliosis and to reduce the rate of progression of contractures when the child becomes wheelchair dependent. When callipers are no longer practical, standing in an appropriate self-hoisting, standing frame can be beneficial. A spinal brace should be provided where there is scoliosis.

Older children should be examined regularly by specialists with expertise in the late stage complications of the disorder such as respiratory and cardiac failure.


Some parental concerns that could lead to DMD diagnosis:

These are a variety of symptoms experienced by various families. Not all boys have the same problems although later difficulties with climbing, getting up from the floor and not being able to walk without tripping are common.

 

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