What is Duchenne Muscular Dystrophy?
What is Duchenne muscular dystrophy?
Duchenne muscular dystrophy (DMD) is a rapidly progressive form of muscular dystrophy that occurs primarily in boys. It is caused by an alteration (mutation) in a gene, called the DMD gene that can be inherited in families in an X-linked recessive fashion, but it often occurs in people from families without a known family history of the condition. Individuals who have DMD have progressive loss of muscle function and weakness, which begins in the lower limbs. The DMD gene is the second largest gene to date, which encodes the muscle protein, dystrophin. Boys with Duchenne muscular dystrophy do not make the dystrophin protein in their muscles.
Duchenne muscular dystrophy affects approximately 1 in 3500 male births worldwide. Because this is an inherited disorder, risks include a family history of Duchenne muscular dystrophy.
What are the symptoms of Duchenne muscular dystrophy?
The symptoms usually appear before age 6 and may appear as early as infancy. Typically, the first noticeable symptom is delay of motor milestones, including sitting and standing independently. The mean age for walking in boys with Duchenne muscular dystrophy is 18 months. There is progressive muscle weakness of the legs and pelvic muscles, which is associated with a loss of muscle mass (wasting). This muscle weakness causes a waddling gait and difficulty climbing stairs. Muscle weakness also occurs in the arms, neck, and other areas, but not as severely or as early as in the lower half of the body.
Calf muscles initially enlarge and the enlarged muscle tissue is eventually replaced with fat and connective tissue (pseudohypertrophy). Muscle contractures occur in the legs, making the muscles unusable because the muscle fibers shorten and fibrosis occurs in connective tissue. Occasionally, there can be pain in the calves.
Symptoms usually appear in boys aged 1 to 6. There is a steady decline in muscle strength between the ages of 6 and 11 years. By age 10, braces may be required for walking, and by age 12, most boys are confined to a wheelchair. Bones develop abnormally, causing skeletal deformities of the spine and other areas.
Muscular weakness and skeletal deformities frequently contribute to breathing disorders. Cardiomyopathy (enlarged heart) occurs in almost all cases, beginning in the early teens in some, and in all after the age of 18 years. Intellectual impairment may occur, but it is not inevitable and does not worsen as the disorder progresses.
Few individuals with DMD live beyond their 30s. Breathing complications and cardiomyopathy are common causes of death.
What is the treatment for Duchenne muscular dystrophy?
There’s currently no cure for muscular dystrophy (MD), but a variety of treatments can help to manage the condition.
As MD progresses, it weakens muscles and mobility and strength is gradually lost. These physical problems can be helped with the following:
- low-impact exercise, such as swimming
- Physiotherapy can be useful for maintaining muscle strength, preserving flexibility and preventing stiff joints.
- Physical aids, such as a wheelchair, leg braces or crutches, which can help standing and staying mobile.
- Occupational therapy can help maximise or improve independence by using different techniques, changing environment and providing any necessary assistive equipment.
Once the chest muscles become too weak to control breathing properly, machines may be needed to assist with breathing and coughing, particularly while sleeping.