Duchenne muscular dystrophy: what it is, causes and symptoms

We speak of muscular dystrophy to refer to a group of diseases that cause the progressive deterioration of the muscles, causing them to become weak and rigid. Duchenne muscular dystrophy is one of the most frequent of this group of disorders.

In this article we will describe what Duchenne muscular dystrophy consists of, what causes it, what are its most characteristic symptoms and how they can be treated and alleviated from a multidisciplinary perspective.

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What is Duchenne muscular dystrophy?

Pseudohypertrophic or Duchenne muscular dystrophy is a degenerative disease of muscles. As the affectation progresses, the muscle tissue weakens and its function is lost until the person becomes totally dependent on their caregivers.

This disorder was described by the Italian doctors Giovanni Semmola and Gaetano Conte in the first half of the 19th century. However, its name comes from the French neurologist Guillaume Duchenne, who examined the affected tissue at the microscopic level and described the clinical picture in 1861.

Duchenne disease is the most common type of childhood muscular dystrophy, affecting 1 in 3600 male children, while it is rare in women. There are nine types of muscular dystrophy, a condition that gradually weakens and stiffens muscles.

The life expectancy of people with this disorder is about 26 years, although medical advances allow some of them to live more than 50 years. Death usually occurs as a result of breathing difficulties.

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Signs and symptoms

Symptoms appear in early childhood, between the ages of 3 and 5. Children with this disease initially have increasing difficulty standing and walking due to involvement of the thighs and pelvis. To stand up, they often have to use their hands to keep their legs straight and lift themselves up.

Pseudohypertrophy characteristic of Duchenne dystrophy occurs in the muscles of the calves and thighs, that are enlarged at the time the child begins to walk due, basically, to the accumulation of fats. This developmental milestone usually occurs late in Duchenne cases.

Later the weakness will generalize to the muscles of the arms, neck, trunk and other parts of the body, causing contractures, imbalance, gait disturbances and falls frequent. The progressive muscular deterioration causes that towards the beginning of puberty the children diagnosed lose the ability to walk and are forced to use a wheelchair.

Lung and heart problems are common as secondary signs of muscular dystrophy. Respiratory dysfunction makes coughing difficult and increases the risk of infection, while cardiomyopathy can lead to heart failure. Sometimes scoliosis (abnormal curvature of the spine) and intellectual disability also appear.

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Causes of this disease

Duchenne muscular dystrophy is caused by a mutation in the gene that regulates dystrophin transcription, a fundamental protein for maintaining the structure of muscle cells. When the body cannot adequately synthesize dystrophin, muscle tissues progressively deteriorate until they die.

The wasting of the muscles occurs as a consequence of the intensification of oxidative stress reactions, which damages the muscle membrane until causing the death or necrosis of its cells. Later the necrotic muscle is replaced by adipose and connective tissue.

This sickness it is more common in men because the gene that causes it is located on the X chromosome; Unlike women, men have only one of these chromosomes, so their defects are less likely to be corrected spontaneously. Something similar happens with some forms of color blindness and hemophilia.

Although 35% of cases are due to “de novo” mutations, usually the genetic alterations typical of Duchenne muscular dystrophy are transmitted from mothers to children. Males who carry the defective gene have a 50% chance of developing the disease, while it is rare in girls and when this happens the symptoms are usually milder.

Treatment and intervention

Even if no treatments have been found to cure Duchenne muscular dystrophy, multidisciplinary interventions can be very effective in delaying and reducing symptoms and in increasing the quality and life expectancy of patients.

Among the pharmacological treatments of this disease highlights the use of corticosteroids such as prednisone. Some studies suggest that taking these drugs prolongs the ability to walk for an additional 2 to 5 years.

Regular practice of physical therapy and gentle exercise (such as swimming) can limit the deterioration of the muscles, since inactivity enhances its affectation. Likewise, the use of orthopedic instruments such as supports and wheelchairs increases the level of independence of patients.

Due to the association of Duchenne dystrophy with heart and respiratory problems, it is important that diagnosed people visit cardiologists and pulmonologists with some frequency. The use of beta-blocker drugs and assisted breathing apparatus it may be necessary in many cases.