Duchenne Muscular Dystrophy

Definition

Duchenne muscular dystrophy is an inherited disorder that involves rapidly worsening muscle weakness.

Alternative Names

Pseudohypertrophic muscular dystrophy; Muscular dystrophy - Duchenne type

Causes, incidence, and risk factors

Duchenne muscular dystrophy is a rapidly-worsening form of muscular dystrophy. Other muscular dystrophies (including Becker's muscular dystrophy) get worse much more slowly.

Duchenne muscular dystrophy is caused by a defective gene for dystrophin (a protein in the muscles). However, it often occurs in people without a known family history of the condition.

Because of the way the disease is inherited, males are more likely to develop symptoms than are women. The sons of females who are carriers of the disease (women with a defective gene but no symptoms themselves) each have a 50% chance of having the disease. The daughters each have a 50% chance of being carriers.

Duchenne muscular dystrophy occurs in approximately 1 out of every 3,600 male infants. Because this is an inherited disorder, risks include a family history of Duchenne muscular dystrophy.

Symptoms

Symptoms usually appear before age 6 and may appear as early as infancy. They may include:

* Fatigue

* Mental retardation (possible, but does not worsen over time)

* Muscle weakness o Begins in the legs and pelvis, but also occurs less severely in the arms, neck, and other areas of the body

o Difficulty with motor skills (running, hopping, jumping)

o Frequent falls o Rapidly worsening weakness

* Progressive difficulty walking

o Ability to walk may be lost by age 12 By age 10, the person may need braces for walking. By age 12, most patients are confined to a wheelchair. Signs and tests A complete nervous system (neurological), heart, lung, and muscle exam may show:

* Abnormal heart muscle (cardiomyopathy)

* Congestive heart failure or irregular heart rhythm (arrhythmias) -- rare

* Deformities of the chest and back (scoliosis)

* Enlarged calf muscles, which are eventually replaced by fat and connective tissue (pseudohypertrophy)

* Loss of muscle mass (wasting)

* Muscle contractures in the heels, legs

* Muscle deformities

* Respiratory disorders, including pneumonia and aspiration of food or fluid into the lungs (in late stages of the disease) Tests may include:

* Electromyography (EMG)

* Genetic tests

* Muscle biopsy

* Serum CPK