muscular dystrophy

Synonyms

Muscular atrophy, progressive muscular dystrophy; Duchenne muscular dystrophy, Becker-Kiener dystrophy, myotonic dystrophy, fazio-scapulo-humeral muscular dystrophy, FSHD

Summary

Muscular dystrophies are congenital disorders of the musculature that lead to a progressive loss of muscle mass and increasing weakness through a disruption in the construction and / or metabolic processes of the muscles. So far, more than 30 different types of muscular dystrophy are known, which are prevalent in symptomatology, frequency, course and prognosis z. T. clearly distinguish. For many muscular dystrophy disorders, the underlying genetic defect is known, which allows a genetic diagnosis (examination of the genome) is possible.
A causal therapy for muscular dystrophy does not yet exist, so symptomatic therapies are in the center, which should mitigate the consequences of the disease and improve the quality of life of those affected.

definition

The term muscular dystrophy summarizes innate diseases of the musculature, which lead to a progressive loss of muscle mass and number and attract attention by weakness of the affected muscle groups (muscle wasting). So far, over 30 different types of muscular dystrophy are known, which differ in inheritance, affected muscle parts, onset of symptoms and severity of clinical course. Some muscular dystrophies also affect the heart muscles.

Forms of muscular dystrophy and characteristics

  • Type Duchenne: Early onset, involvement of the heart muscle, severe course, most common form, almost exclusively boys affected.
  • Type Becker-Kiener: Similar symptoms as in Duchenne muscular dystrophy, but later onset, somewhat milder, also almost exclusively affected boys
  • Fazio-Skapulo-Humeral Muscular Dystrophy: Mild form, beginning in young adulthood, initially affects the musculature of the shoulder girdle and the face, men and women are equally affected.

frequency

Overall, the frequency of muscular dystrophies is estimated at 1: 2000 to 1: 5000, while the individual muscular dystrophy disorders show differences in heredity and frequency in the population. Of the above, the Duchenne (about 1: 5000) and Becker-Kiener muscular dystrophy (about 1: 60000) belong to the x-linked recessive inherited diseases and therefore affect almost exclusively boys or men. The fascio-scapulo-humeral muscular dystrophy (about 1: 20000), however, is inherited as an autosomal dominant, so men and women are equally affected.

causes

The causes of progressive muscle wasting and weakness are congenital defects in muscle cell structure and muscle metabolism. In many muscular dystrophies, however, the exact mechanism of the disease is not yet clear.

symptoms

The affected persons stand out due to an increasing weakness of affected parts of the body, which may possibly give indications of the underlying form of the muscular dystrophy by the localization.
In contrast to other diseases that manifest in weakness or muscle wasting (eg diseases of the nerves or spinal cord, spinal canal stenosis), muscular dystrophies maintain muscle reflexes and sense of touch. If the heart muscle is affected, it leads to a heart failure (heart failure), the infestation of the respiratory muscles leads to respiratory distress and favors respiratory infections (eg pneumonia).

The onset of symptoms varies considerably between the individual forms: while severe forms such as Duchenne muscular dystrophy are already noticeable in childhood, more benign forms may not be seen until adulthood. B. diagnosed as a cause of incorrect posture.

diagnostics

The basis of the diagnosis is the question of the occurrence of similar complaints among family members (family history) to ensure the suspicion of an inherited disease. Only in the rarest cases does a muscular dystrophy occur spontaneously (so-called "new mutation"). The physical examination reveals the weakness and reduction ("atrophy") of affected muscles with largely preserved muscle reflexes and absence of, for example, emotional disorders or involuntary muscle twitching. The distribution of muscle weakness and shrinkage on certain parts of the body can already provide important diagnostic information. In the blood test, an increase of muscle enzymes (substances from the muscle cells) can be noticed, which suggest damage to muscle cells, but this is diagnostically of minor importance.

To differentiate from other diseases that may clinically produce a similar picture, further diagnostic steps may be initiated. Here, especially diseases of the nerves and spinal cord and the neuromuscular end plate, the interface between nerve and muscle, must be excluded. The serve z. B the recording of nerve conduction velocity (NLG) and electrical muscle activity (electromyography, EMG).
The microscopic examination of a sample of affected musculature (muscle biopsy) taken during a small surgical procedure shows a characteristic picture in all forms of muscular dystrophy, which differs from that in the case of muscular dystrophy. B. differs from nerve diseases.

Finally, in the case of many muscular dystrophies, specific changes in the genotype of those affected are known and can be detected by special diagnostic procedures. This can be done in human genetic centers of larger hospitals.

differential diagnoses

Muscle weakness and atrophy can be symptoms of a number of other conditions that may need to be ruled out. These include above all:

  • Diseases of the nerves and the spinal cord, z. As poliomyelitis ("polio"), amyotrophic lateral sclerosis or multiple sclerosis. The exclusion is based on clinical picture, measurement of nerve conduction velocity and electrical muscle activity, which differ from the findings in a muscular dystrophy. Also, a muscle biopsy can provide information on the basis of a nerve damage.
  • Diseases of the "neuromuscular end plate", the nerve-muscle interface caused by autoimmune processes. These include myasthenia gravis or the Lambert-Eaton syndrome, which can also occur in the wake of tumor diseases. Here, too, there are characteristic differences in the electromyogram, the nerve conduction velocity and the muscle biopsy. Autoantibodies that would be detectable in the blood and the microscopic specimen in the abovementioned disorders are absent in muscular dystrophies.

therapy

To date there is no causal therapy for muscular dystrophies. So far, attempts at drug therapy with a variety of substances have all been disappointing. For the future, the hopes lie in a genetic therapy that solves the underlying defects in the genome or their effects in muscle metabolism, but are currently such attempts at best in the initial stages.

Therefore, the treatment of muscular dystrophies is currently based on supportive measures designed to cushion the effects of increasing muscle weakness and help patients cope with everyday life. Above all, this includes physiotherapy to maintain the greatest possible mobility and to prevent malpractices.
Physical training should be done very carefully to prevent damage to the muscles due to overloading.
The use of anabolic steroids should be discouraged on the basis of serious side effects and unproven use and, if necessary, in exceptional cases, under the close control of a specialist physician. Psychotherapeutic care can help sufferers manage their lives by diagnosing a chronic progressive illness, and contact with one of the numerous support groups can facilitate access to services. As with all hereditary diseases, human genetic counseling is recommended for further family planning; the purpose and benefit of prenatal diagnosis must be decided on a case-by-case basis.

Forecast:

The prognosis depends largely on the involvement of the heart and respiratory muscles and is thus quite different between the various muscular dystrophies. While z. For example, if the Duchenne type leads to death due to heart failure or respiratory tract infections at a young age, life expectancy is not impaired in more benign forms. However, even mild forms of muscular dystrophy in the course of the disease sometimes lead to severe impairments in everyday life and quality of life.


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