Duchenne Muscular Dystrophy

Duchenne uscular dystrophy is also known as the Duchenne's disease. It is an inherited condition affecting body muscles that maifest in childhood, slowly progresses and having fatal consequences in the end.

Causes

The cause is a faulty gene of a muscle protein known as dystrophin. Dystrophin is necessary for muscle cells that succumb to atrophy and necrosis when dystrophin is missing. The defective gene is located in X chromosome and that is why Duchenne muscular dystrophy affects only boys (it is the same way of genetic inheritance as in hemophilia) and its occurrence in girls is virtually impossible. The disease may have a positive family history but it is not the rule.

Symptoms

The affected child is born without any symptom ad he seems to be completely healthy. However, in the childhood between 2-6 years of age, first signs of missing dystrophin occur.

 

Muscle cells die and they are replaced by fibrous tissue. The disease manifests with slowly progressive muscle weakness, the child has got problems when running and climbing stairs and has difficulties when getting up from horizontal or sitting position. The process progresses and in few years it makes a wheelchair use necessary. In addition to progressive muscle paralysis, the boys have abnormally large calves. This calf enlargement is caused by deposition of connective tissue that replaces the disappearing muscle fibers. The most serious complication is impairment of the respiratory system due to the breathing muscles disorders. Shortness of breath gradually occurs and worsens; it is accompanied with recurring respiratory infections including pneumonias. In the last stages of illness mechanical ventilation is usually needed. The disease is fatal and the direct causes of death are the above-mentioned recurring respiratory infections. The majority of patients die before 30 years of age.

Diagnosis

The suspicion is often stated by a pediatrician who discovers mobility disorders and muscle weakness in a boy. Positive family history of Duchenne muscular dystrophy has also a great importance. Electromyography should be performed to evaluate muscle strength. Blood tests allow us to check the level of an enzyme known as creatine kinase. The creatine kinase is released from the decaying muscle fibers and its concentration is elevated in a patient with Duchenne muscular dystrophy. A muscle biopsy may be performed to obtain a sample of the muscle tissue for further investigation – such examination confirms the missing dystrophin.

Treatment

The disease can not be cured. The physicians focus on improving the patient's life and treating the symptoms and complications. Regular rehabilitation can help to slower the disease progress. Supportive equipment as the wheelchair may be used and artificial lung ventilation is often necessary in last stages of the disease. Frequent pneumonias are treated with antibiotics.

 

Note: There is also a milder form of the disease known as Becker's disease or Becker muscular dystrophy. The main difference is that in Becker muscular dystrophy the dystrophin is not missing but its concentration is reduced. Becker muscular dystrophy manifests later, usually in 10-12 years of age and it has slightly better prognosis than Duchenne dystrophy.