Named after Dr. Duchenne de Boulogne, Duchenne muscular dystrophy is a genetic condition marked by degeneration of the muscles. It is a part of a group of 20 hereditary conditions known as muscular dystrophy and Duchenne muscular dystrophy is the most common. It is more prevalent in males than females.
Duchenne muscular dystrophy is caused due to genetic defect which adversely affects the production of a protein known as dystrophin. The protein occurs in muscle fibers; low levels of this protein causes weakness of the membranes that surround the muscles, thereby increasing its risk to easy wear and tear and eventual death of the muscle fibers.
The muscles of the hips, trunk, and shoulders typically become weaker in affected children, leading to reduced walking abilities. The condition may not be noticeable at birth, but the weakness of the fibrous tissues can be easily seen as the infant grows. The life expectancy of the affected child is dependent on the severity of the associated cardiac and respiratory complications.
About 1 in every 3600 children are at risk to developing the genetic mutation responsible for Duchenne muscular dystrophy. The defective gene is passed by the mother in about 2/3rd of the cases while a new defect occurs in the rest 1/3rd of the cases. Every child is at risk to developing the condition, but those with a family history of the condition are especially vulnerable.
Duchenne muscular dystrophy is one of the most serious forms of muscular dystrophy as the symptoms and associated health complications tend to deteriorate rapidly. The signs and symptoms of Duchenne muscular dystrophy can be easily seen from a very early age, between 1 and 4 years of age. They include:
- Weakness of the tendons and the muscles, especially in body areas such as the calf, hips, thighs, shoulders, and pelvis. It can pose problems in walking, hopping, jumping, running, and/or climbing stairs.
- Muscles tissues in the tongue may get replaced by connective tissues and fat. This can cause enlargement of the tongue causing speech abnormalities.
- Weakness of the shoulder tendons may cause the child to slip when held in the arms.
- The calf muscles gain excessive bulk but do not possess any strength. This can pose difficulties in getting up; the child may use his hands to get up. Using the hands to support the legs when getting up can cause the child to experience increased incidences of falls.
- Increased weakness of the trunk muscles may trigger abnormal development of the skeleton. It is possible for the spine to curve abnormally resulting in scoliosis.
- Walking and other developmental milestones may occur later than usual. Affected children may exhibit a characteristic waddling walking style.
- Increased tiredness and exhaustion.
- The ability to walk may be completely lost by age 12, thereby confining the patient to a wheelchair.
- The diaphragm and cardiac muscles may also experience weakness triggering a case of cardiomyopathy. Almost all patients develop the cardiac condition by age 17 to 18. The intensity and quickness of the progression of Duchenne muscular dystrophy symptoms, especially cardiac and respiratory problems, determine the life expectancy of the patient. In most cases, the average lifespan is about 29 to 31 years.
Causes of Duchenne muscular dystrophy
Duchenne muscular dystrophy is a hereditary disorder caused due to mutation of a gene responsible for the functioning of a protein known as dystrophin. The protein is vital to maintenance of the health of muscle cells. Most individuals with Duchenne muscular dystrophy do not have a large section of the associated gene, leading to lowered production of dystrophin. Subsequently, there is dissolution of the muscle cells, increased weakness and ineffectiveness of the muscle fibers, and their eventual death.
The genetic defect associated with Duchenne muscular dystrophy is passed in an X chromosome-linked recessive method. It may be noted that children get the X chromosome from the mother and the Y chromosome from the father. Girls have two copies of X chromosomes wherein one X chromosome copy is free from the genetic mutation. Thus, girls are less vulnerable to the effects of the genetic defect. On the other hand, boys just have just one copy of the X chromosome and hence at greater risk to the effects of the genetic mutation.
Anyone can develop the genetic defect and subsequently Duchenne muscular dystrophy. However, people with a family history of the condition are at increased risk to developing it.
People, especially women, with a family history of Duchenne muscular dystrophy need to undergo a DNA test to verify whether they are carriers of the genetic defect before planning to start a family.
If a child shows all the signs and symptoms of Duchenne muscular dystrophy as stated above, then parents need to consult a doctor for diagnosis. Duchenne muscular dystrophy diagnostic tests include:
- Creatine kinase test: Patients typically have increased amounts of creatine kinase, a muscle enzyme. Hence, its levels are checked.
- Genetic tests: The diagnosis is confirmed after some blood tests and a DNA test. Genetic testing will help verify the occurrence of defects in the dystrophin associated gene.
- Echocardiogram and other cardiac tests: Is done to determine an underlying cause of cardiomyopathy.
- Electromyography and muscle biopsy: To check the levels of dystrophin protein and the extent of muscle weakness and muscle damage.
- Other tests: Tests to check the occurrence of any spinal and skeletal abnormalities. Tests to check for pulmonary and respiratory problems such as pneumonia, etc.
Treatment of Duchenne muscular dystrophy
There is no cure for Duchenne muscular dystrophy. Treatment is focused on alleviating and managing the signs and symptoms.
- Physical therapy such as massage therapy, breathing exercises, swimming and other physical exercises, etc. to improve the strength of the muscles and prevent their physical deterioration.
- Steroids and other medications to decrease the severity of the symptoms, improve muscle strength, and enhance the range of motion.
- Occupational therapy to improve the social and work life of the patients, and to train them to carry out the daily activities on their own. It may include the use of medical equipment like splints, braces, etc. as well as psychological therapies and emotional support to boost self-esteem.
- Diet control to maintain the weight.
- Stem cell therapy, gene replacement, and exon skipping are treatment options that are still in the research stages.
- Regular heart and respiratory function checkups and associated treatments.
Duchenne muscular dystrophy – life expectancy
The average life expectancy is about 25 to 35 years. Some patients may live till the mid-forties via use of cardiac medications, ventilator support, etc.