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Duchenne disease. Duchenne muscular dystrophy. Hereditary diseases. What is Duchenne muscular dystrophy


What is Duchenne muscular dystrophy?

There are many types of muscular dystrophy, all of which are caused by problems with genes (the units of heredity passed from parents to children). In Duchenne muscular dystrophy (DMD), a lack of the protein dystrophin causes muscle deterioration and destruction, leading to progressive difficulty in walking and overall mobility. DMD is the most common and one of the most rapidly progressive childhood neuromuscular diseases. Approximately every 3000th newborn boy in the world suffers from this disease. DMD affects only boys (with very rare exceptions).

How is Duchenne muscular dystrophy inherited?

In Duchenne muscular dystrophy, the defective gene is X-linked. This means that this gene is located on the X chromosome. Women have two X chromosomes, and men have one X chromosome, which they inherit from their mother, and one Y chromosome, which they inherit from their father. In about two-thirds of cases, the defective gene is passed on to the son via the mother's defective X chromosome. In these cases, the mother is a “carrier” who, in most cases, does not show any symptoms of the disease. This is because the gene is “recessive,” which means that her normal X chromosome will be dominant and produce dystrophin normally. Only a very small number of carriers have a moderate degree of muscle weakness, which is usually limited to the shoulders and hips, and these women are called "emerging carriers". The genetic disorder may have arisen in a previous generation in which there was a family predisposition to the disease. However, in about one-third of DMD cases, the genetic disorder occurs in the boy himself, and is then called a “spontaneous mutation.”

Why is genetic counseling so important?

Each son of a female carrier has a 50% chance of inheriting DMD from his mother's defective X chromosome, and each daughter has a 50% chance of becoming a carrier of the disease in the same way. Immediately following a diagnosis of DMD, genetic counseling should be obtained, as well as appropriate testing for family members who may be carriers. During the consultation, you will receive information about the sequence of heredity and the danger to other family members, as well as the “prognosis” (possible consequences of the disease). Information about diagnostic testing, including prenatal testing and carrier testing, is also provided during this consultation.

How is DMD diagnosed?

Symptoms

DMD is often difficult to diagnose because symptoms vary and if there is no family history of the disease, DMD may not be suspected. It is quite common to experience a delay in the onset of walking when the child takes his first steps at approximately eighteen months. When walking, a boy with DMD may often fall. He often has difficulty climbing stairs, has difficulty running and jumping, and may develop a duck-like gait. The classic symptom is enlargement (hypertrophy) of the calf muscles, which occurs in approximately 90% of cases. He may develop a tendency to walk on his toes, which is often accompanied by a protruding belly and splayed legs at the knees, called "lordosis." He may have difficulty getting up from the floor without assistance. To help himself, he may climb his legs with his hands - this is called the “Goverz sign.” These symptoms usually begin to develop between the ages of one and three and continue to progress until he needs a wheelchair, most often between the ages of eight and twelve.

Creatine phosphokinase assay
Laboratory testing for DMD begins with testing a muscle enzyme called creatine phosphokinase. Due to the lack of dystrophin in the muscle fibers, creatine phosphokinase leaks from the damaged muscle and appears in the blood in large quantities. A blood test may show creatine phosphokinase levels 50 to 100 times higher than normal. Although this enzyme is often slightly elevated in other types of dystrophy (including Becker's associated muscular dystrophy), it is much higher in DMD. Approximately 70% of DMD carriers will also have slightly elevated creatine phosphokinase levels. Therefore, a high level of creatine phosphokinase indicates that the muscles themselves are a likely cause of weakness, but does not tell us with a 100% guarantee what kind of muscle disease it may be.

DNA Study
Currently, in order to establish the exact DNA, DNA is being studied using new technologies. Genes are made up of segments of DNA (deoxyribonucleic acid), and the corresponding portions of this genetic material can be examined using a microscope. The abnormalities that cause DMD can be of three types: deletion (missing parts), duplication (extra parts), or point mutation (changed parts). DNA testing is often time-consuming and technically difficult and, depending on the genetic defect, can produce uncertain results. In some cases, these studies can provide accurate information about the genetic abnormality that causes DMD, but in other cases the abnormality cannot be accurately identified. This also applies to the diagnosis of female carriers. DNA testing may also be done before birth in an unborn child if there is a history of the disease in the family.

Muscle biopsy
If DNA testing does not provide a clear picture, a muscle biopsy may be required. A small piece of muscle tissue, usually from the thigh, is removed using a needle. Using a special staining method in the laboratory, muscle tissue is examined under a microscope for the presence of dystrophin. In DMD, the test shows the absence of dystrophin, while in the related disease Becker muscular dystrophy, small amounts of dystrophin are present. Therefore, muscle biopsy analysis is necessary to establish an accurate test in cases where it is not known whether anyone in the family has had the disease, or when DNA testing is inconclusive.

Only two diseases can cause difficulties in diagnosing DMD: Becker muscular dystrophy and limb-girdle muscular dystrophy. The above tests, especially muscle biopsy, can differentiate between these diseases.

Is DMD curable?

There is currently no cure for DMD, but extensive research in this area continues around the world. Researchers have made significant progress in understanding DMD and continue to search for a cure. Some areas that research is currently focusing on are:

Duchenne muscular dystrophy

Penny Southall, Dan Hanson's mom

“My son Dan was diagnosed with Duchenne muscular dystrophy at the age of three. I know from experience what a crushing blow such a diagnosis can be.
“Just like us, you must be trying to figure out how you can even come to terms with this. We found our way to cope, and you can too. I told myself that he was still the same person, but I saw him from a different side. This thought helped me move forward. If he feels good, then I will feel good too.
“When I learned of Dan’s diagnosis, the first thing I did was look for research into what life is like for people with Duchenne muscular dystrophy. I learned that he can live as full and happy a life as anyone else. At that moment, this became a great consolation for me, and years later, I was already convinced of this.
“Dan has close friends, is a good student, plays sports and is confident about his future. Nowadays, so much help and support is provided to people with disabilities. They can try themselves in sports and get the necessary education.
“I asked my son, now 15, what he would like to say to families who received news of this diagnosis. He replied, “It seems terrible at first, but it will get better.”

What is Duchenne muscular dystrophy?

Duchenne muscular dystrophy is muscle atrophy caused by a lack of a protein called dystrophin. Usually only boys are affected by this disease. Around 100 boys with Duchenne muscular dystrophy are born in the UK each year, and there are currently 2,500 boys and young people with Duchenne muscular dystrophy in the UK. There is a risk that out of 3500-5000 male babies, one will have Duchenne muscular dystrophy.

Duchenne muscular dystrophy is a serious disease that causes progressive muscle weakening. Due to a lack of dystrophin, muscle fibers weaken and give way to fibrous or fatty tissue, causing gradual muscle breakdown.

What are the causes of Duchenne muscular dystrophy?

Duchenne muscular dystrophy is a genetic disorder caused by an abnormality or mutation in the genetic code (DNA). In Duchenne muscular dystrophy, a mutation occurs in a gene called dystrophin and which is located on the X chromosome or sex chromosome (girls have two X chromosomes, boys only one). In half of cases, the disease is transmitted from the mother who is the “carrier,” but it can also result from a new mutation in the child’s genes.

If a mutation occurs in a woman’s body, she is called a “carrier.” Female carriers are usually not affected by this disease because they have a second X chromosome where dystrophin can be produced. A small number of women have some degree of muscle weakness and are called "clear carriers".

Each son of a carrier has a 50% risk of developing the disease, and each daughter has a 50% risk of being a carrier.

Genetic counseling and screening of other family members for risk of being carriers should occur as soon as possible once a boy is diagnosed with Duchenne muscular dystrophy. You can contact your consultant doctor or family doctor.

How is Duchenne muscular dystrophy recognized?

Most boys with Duchenne muscular dystrophy are not diagnosed with Duchenne muscular dystrophy until symptoms appear, unless there is a family member with the condition. The first signs of Duchenne muscular dystrophy usually appear between the ages of one and three years and are usually associated with impaired muscle function. Boys may start walking later than their peers, fall more often, or have difficulty running, jumping, or climbing. They may have enlarged calf muscles.

Some boys with Duchenne muscular dystrophy have slow speech, which may be the first sign of the disease. A blood test reveals high protein content entitled creatine kinase(KK). KK usually appears in the muscles, but when they are damaged, as is the case with Duchenne muscular dystrophy, it enters the blood. Liver enzymes(aminotransferases, ALT and AST) are also often found at a high level, as a consequence of muscle damage, not liver damage.

Duchenne muscular dystrophy must be confirmed genetic blood test. Different types of genetic tests provide specific and detailed information about DNA mutations.

Genetic confirmation of the disease is critical. This allows families to conduct prenatal diagnosis in future pregnancies, as well as screen other family members in case they carry a mutation in the dystrophin gene. Moreover, genetic testing will help determine whether a boy is eligible to participate in a clinical trial that is starting or planned.

Your doctor may also advise needle biopsy of muscles, where a small sample of muscle is taken for analysis. Such studies can provide information about how much dystrophin protein is present in muscle cells, and in some cases help distinguish Duchenne muscular dystrophy from a milder form of the disease known as Becker muscular dystrophy. However, clinical signs and genetic analysis are usually sufficient to distinguish the two forms, without the need for a muscle biopsy.

Is there a treatment or cure?

No cure has yet been discovered for this disease, but there is encouraging research in this area. A multi-professional approach, including physiotherapists and occupational therapists ( occupational therapists – specialists who help people with disabilities get used to life) is the best way to control Duchenne muscular dystrophy.

Having access to specialists from a variety of disciplines is vital to providing a person with Duchenne muscular dystrophy with all the comprehensive support they need. This means that the patient should have the opportunity to consult with specialists in different fields during one visit to a specialized center: receive advice on the respiratory system, cardiovascular system and physiotherapy. By working together, these professionals will provide more effective care.

It is important to have regular check-ups with specialists in order to make decisions about new treatments at the most appropriate time, and perhaps anticipate and prevent problems. It is recommended that you see your primary care physician every six months and your physical therapist every three to four months.

Steroids ( prednisone or deflazacort) are often prescribed for Duchenne muscular dystrophy, as they slow down for some time the process of muscle weakening and impaired mobility and prevent or delay the development of complications. However, there are many possible side effects that need to be carefully monitored.

Other drugs for Duchenne muscular dystrophy have begun to emerge, including Translarna(ataluren), which is currently available in some European countries and may slow the progression of symptoms in boys with Duchenne muscular dystrophy. Translarna only affects a small group of boys who are carriers of a specific mutation in the dystrophin gene ( "nonsense" mutation, where a point mutation in the DNA sequence results in a stop codon). Your doctor will tell you whether this medicine will be effective for your son. Other treatments for specific mutations may soon be approved.

Intensive research into possible treatments for Duchenne muscular dystrophy continues. Some drugs are currently undergoing clinical trials.

It is helpful to have a copy of the genetic report (showing the type and location of the dystrophin gene mutation found in your child). This will help determine which medicine or trial is best for your child.

The Duchenne Muscular Dystrophy Registry will provide up-to-date information on the progress of clinical trials and can help determine which children are likely to be eligible for specific clinical trials. Your doctors will tell you how to register your child on this registry.

The North Star Adult Network, made up of expert neuromuscular disease consultants, allied health professionals, Duchenne muscular dystrophy patients themselves and Muscular Dystrophy UK, works to improve standard care and support for adults across the UK. Kingdoms. There is also a pediatric version, the North Star Project, which works to improve care for children with Duchenne muscular dystrophy.

If you would like to find out more about the team's latest research, please contact the Research Department on: 020 7803 4813 or by mail: [email protected].

What's the forecast?

In the early stages, boys with Duchenne muscular dystrophy show signs of muscle weakness, such as difficulty running, jumping, climbing stairs or from the floor. They can move in a Gower manner (having to support themselves with their hands on their hips when rising from the floor) and waddle (on their toes and with an arched lower back).

As muscle weakness develops, boys find it more difficult to walk as fast or as far as other children and may begin to fall. They can still climb stairs, but with their second foot next to the first.

Later, when walking becomes more difficult, boys will find it difficult to climb stairs or get up from the floor.

Steroids significantly change the course of the disease. They help restore muscle strength over a period of time and delay the time when boys may need a wheelchair.

Predicting when a patient will start using a wheelchair is difficult because each case is different.

However, the need for a wheelchair usually occurs between the ages of 8 and 11 (sometimes earlier, sometimes later). At first it will only be needed for long distances. Later the chair will be used constantly. At this stage, boys may have difficulty raising their arms above their shoulders.

With further development of muscle weakness, it becomes more difficult to maintain body position, and complications may arise. The disease is serious and can shorten life expectancy, but now, with high standards of care, most young men with muscular dystrophy reach adulthood.

Some boys with Duchenne muscular dystrophy may have learning and/or behavior difficulties as a result of the disease's effects on the brain. Learning difficulties in Duchenne muscular dystrophy do not progress, but it is important to recognize them immediately and report them (for example, to school) to ensure your child has the support they need to develop skills and achieve full learning.

Family support is essential, and some behavioral and learning differences should be reported to professionals.

Original: Duchenne muscular dystrophy

Translation: Zoya Mazurova

Duchenne-Becker muscular dystrophy is a common form among neuromuscular diseases that are inherited. Dystrophy is represented by degenerative changes in muscle tissue.

The disease occurs due to a mutation in the gene encoding the synthesis of the dystrophin protein. A large amount of protein is located in the sarcolemma area. When structural changes occur in the sarcolemma, the components of the cytoplasm degenerate, followed by the death of myofibrils. The disease has a recessive type of inheritance linked to the X chromosome.

Kinds

From a clinical point of view, Duchenne-Becker muscular dystrophy is divided into Duchenne muscular dystrophy and Becker muscular dystrophy.

Duchenne muscular dystrophy occurs in 3 cases per 10,000 newborns. The disease makes itself felt very early. The first thing that indicates it is that the child begins to walk later, at the age of 2 years does not know how to jump and run, and is noticeably behind his peers.

On examination, muscle weakness is clearly visible. By the age of three, the symptoms are more pronounced, this can be seen in the peculiar gait, the child seems to waddle from side to side. First, the calf muscles atrophy, over time the process spreads to the muscles of the thigh, pelvic, shoulder girdle, gluteal muscles, deltoid muscles, tongue muscles, and so on.

The atrophic process affects organs and some systems. When the heart is involved, acute heart failure develops. In most cases, this process ends fatally. Sick children have reduced intelligence. The last stage of the development of the disease is the appearance of changes in the muscles of the face and respiratory tract. Death occurs at 20-30 years of age.

Laboratory testing of blood serum shows an excessive increase in creatinine phosphokinase.

Becker muscular dystrophy is a form of neuromuscular disease that is benign in nature. This pathology occurs in one case per 20,000 newborns. The symptoms are similar to Duchenne muscular dystrophy, but appear in a less pronounced form.

The onset of the disease occurs at 10-15 years of age, and work capacity remains for 20 years. No cardiomyopathy or decreased intelligence was observed. Fertility is within the normal range.

Causes

The cause of the development of pathology is a violation in the structure of the X chromosome. In the presence of a mutation in the 21st locus of the short arm, muscular dystrophy develops.

In 70% of cases, the development of the disease is caused by the transmission of a defective gene from the mother. In this case, the mother acts as a carrier of the mutation. In the remaining cases, the mutations occur in the mother's egg.

Duchenne dystrophy involves a shift in the frame responsible for reading information from DNA. The integrity of the sarcolemma is disrupted in the absence of dystrophin, the voids are filled with fatty and connective tissues. This disease is manifested by a noticeable decrease in muscle contractility and tone with further atrophy.

Symptoms

Symptoms that appear in men:

  • general weakness body, excessive fatigue in the absence of heavy loads;
  • growing weakness in the legs;
  • problems with rise up the stairs;
  • a large number of manipulation when rising from a sitting position,
  • gait resembles a duck step;
  • robot malfunctions cardiovascular systems, development of arrhythmia;
  • muscular pain in the upper and lower extremities;
  • frequent stumbling and falls when walking;
  • dyspnea when performing physical activity;
  • swelling muscles with increasing load on the body.

At the beginning, the signs that are most often found in patients are given. Muscular dystrophy is most often detected either in childhood or upon reaching adulthood. After forty years, breathing problems develop, as well as disruptions in the functioning of the heart.

Diagnostics

Diagnosis of the disease is carried out depending on its nature. If the pathological gene is inherited from mother to child, then an analysis is performed to determine the amount of serum enzymes.

In infants, during the development of the disease, there is an excessive excess of enzyme levels (fifty times the norm), which return to normal limits as the child grows. As dystrophy progresses, a slight increase in indicators is observed.

Increasing the level of serum enzymes is an unstable process. It all depends on age characteristics, as well as on the degree of damage to the body. Elevated enzymes may develop even before symptoms of the disease appear. Exceeding the normal level of enzyme parameters is not affected by steroid therapy.

In the presence of a hereditary factor, diagnosis is carried out using screening. Exceeding the normal level of serum enzymes in sick children is 5-100 times higher than the upper limit of normal for an adult.

The highest rates are observed in children aged 2 years. As soon as the first symptoms of the disease appear, the rate begins to decline. If the child has a stable indicator, then the presence of the disease can be excluded. The recommended age for analysis is 2-3 months of age.

In the first days of life, the creatine kinase level is high and this is the norm. And it is important to monitor how he will behave further using tests. If a positive test for muscular dystrophy is obtained through a blood test, a plasma test should also be performed.

Creatine kinase more than three times higher than the upper limit is characteristic of Duchenne dystrophy and more than 2 times higher in Becker dystrophy.

Screening for muscular dystrophy in newborn girls has been cancelled. Previously, screening at the 18th week of pregnancy using fetal blood was widely used. Today it is not used, since the probability of a false indicator is very high.

Clinical diagnosis of dystrophy:

  • promotion creatine kinase observed in almost all patients with muscular dystrophy;
  • whey ALD is elevated in approximately 20% of patients;
  • serum indicator LDH increased in 10%.

With normal indications, the diagnosis of dystrophy is simply inappropriate. The highest rates are observed in sick young children, with a gradual decrease every year.

Treatment

To date, no remedy has been developed that can stop the process of muscle atrophy. It is impossible to get rid of it. Treatment of the disease is based on prolonging the motor functions of the body for as long as possible. Treatment can slow down the process, but not completely get rid of it.

If young children have signs indicating possible muscle wasting, they should consult a doctor immediately. The doctor will conduct an examination and also prescribe an examination.

If relatives do not have dystrophy, electromyography is prescribed, which will show how muscles and nerves work. If necessary, a muscle tissue biopsy is performed.

There is certain therapy to improve life. It consists of physical therapy to maintain joint mobility, thereby maintaining their flexibility. Massage improves blood circulation in the affected area, thereby delaying atrophy.

It is necessary to take vasodilators, use auxiliary mobile devices, and special braces that allow you to keep the muscles in a stretched position. Canes, crutches, walkers, and wheelchairs will also help you move independently.

If breathing is difficult, a machine is used to help oxygen enter the lungs. There are orthopedic devices that fix the foot and ankle. They can reduce the risk of falls and make walking easier.

The operation is indicated in the following cases:

  • appearance contractures in tendons;
  • difficulty breathing;
  • irregularities in work hearts, installation of a pacemaker.

If one of your relatives suffered from dystrophy, you should consult a geneticist.

Consequences and complications

This disease has a number of complications and consequences:

  • spine over time deformed;
  • fades away motor ability that leads to a wheelchair;
  • there are frequent inflammatory processes in the respiratory organs;
  • disruptions occur cardiovascular systems;
  • are decreasing intellectual capabilities;

Death occurs both in childhood and later, depending on when the disease developed.

Heredity

Dystrophy is a serious disease that is inherited. Its occurrence does not depend on improper care, insufficient attention or lack of developmental activities.

Preventive measures

Before planning a pregnancy, a woman needs to be examined for the presence of pathological genes in the body. This is necessary in cases where one of the relatives had this disease. Dystrophy can be detected during pregnancy. To do this, amniotic fluid, cells or fetal blood are taken and analyzed.

If a condition occurs that requires immediate medical attention, physicians should be aware of the following factors:

  • Availability the child has Duchenne muscular dystrophy, as well as the medications the child is taking.
  • Trend development diseases.

If your condition worsens due to missing a dose of steroids, you should immediately inform your doctor. Patients suffering from this disease have an increased risk of bone fracture. Fractured limbs usually require surgery.

For successful therapy you will need a specialist in physical therapy. Leaving muscles inactive for a long time has bad consequences. Therefore, an important point is to put the child on his feet as quickly as possible and prevent the muscles from atrophying. If a special device is used to support breathing at night, you must take it with you to the medical facility.

This pathology means a violation of muscle nutrition. This pathology is a hereditary muscle weakness and is extremely rare.

This syndrome usually affects only boys. There is 1 disease per 3000 births of normal babies.

There are other types of muscular dystrophies that occur in girls, but the manifestations there are milder.

During the course of this disease, as it progresses, a disruption of the connections between muscles and nerves occurs.

Duchenne syndrome is inherited; the mother is a carrier of the gene for the described pathology, but is not sick herself.

Other types of dystrophy

In addition to the described syndrome, there are other types of these dystrophies, although they rarely occur.

Becker syndrome is extremely rare, and only males are affected. Pathology occurs at 10-11 years of age and becomes less noticeable at 35-40 years of age.

Hereditary muscular myopathy - affects both girls and boys, also has a genetic cause, and is observed even less frequently than the described syndrome.

Humoscapulofacial myopathy has an extremely long development and a favorable course. Appears before 10 years of age. Characterized by: being in infancy, they cannot suckle the breast well; at a later age it is not possible to make the lips into a tube; It is difficult to lift the arms; the face has a mask-like appearance.

Emery-Dreyfus dystrophy - manifests itself like other types of dystrophies, but unlike the previous ones, these have a bad effect on the heart.

First symptoms

The child walks later, but all his attempts are unsuccessful. The child walks, waddling from one side to the other, often falls on his butt, the desire to get up and get up from a body position sitting on the floor often turns out to be unsuccessful.

The leg muscles may look quite strong, although in reality they are not. All other muscles responsible for walking are poorly developed.

Diagnostics

Seeing characteristic symptoms, the doctor may suspect this pathology in the baby. In this case, the therapist should refer the child to an orthopedist.

Blood test: normal muscle tissue contains creatine phosphokinase. With this pathology, the amount of this enzyme is too high.

Muscle test: Electronic muscle testing measures the speed at which nerve reactions are transmitted to the muscles.

Muscle biopsy: A piece of muscle tissue is examined under a microscope. This study reveals growths in the form of atherosclerotic plaques.

Why is this pathology considered genetic?

This syndrome is a genetic disorder that occurs due to a modified allele on the sex X chromosome.

Every cell of the human body, with the exception of gametes, contains 46 chromosomes. One autosome contains many alleles (about 1000). Alleles and autosomes contain deoxyribonucleic acid, which is responsible for transmitting data that passes from one generation to another.

The structure of the gene is protein. Globulins are a building material for the human body.

This disease appears due to the presence of a specific gene on the X chromosome, which is found in both male and female bodies. The allele responds to the production of a protein that forms normal muscle tissue.

Girls sometimes inherit an altered allele, but usually they do not develop Duchenne disease, since their body has two X chromosomes, one of them, healthy, replaces the disorder in the second.

In the course of certain experiments, the following data were obtained: Duchenne disease in boys can be congenital or acquired due to mutations that occurred in the genotype after birth.

Pathology progression

As the pathology progresses, the symptoms become more pronounced; this happens because the muscles are practically no longer able to facilitate adequate movement. Over time, the hand muscles weaken, and it becomes very difficult for the baby to grasp and hold objects. The muscles of the arms and legs become dystrophic, the joints become stiff. Deformation of the elbow, hip and knee joints often occurs. The muscles that hold the spinal column stop growing, causing the spine to become curved. It is difficult for the baby to walk. Some children do not study well. Learning requires painstaking work, during which the child simply does not keep up with the curriculum.

How to help your baby?

Unfortunately, there is no cure for this syndrome, so it is worth telling your child how to adapt to life with this disease.

The child is indicated for psychotherapy in order to convince him of the importance of physical activity.

It is worth practicing special gymnastics in order to maintain movement in the joints.

To prevent contractures from forming, it is worth using special splints and corsets.

Therapeutic walking is indicated.

Children with this syndrome experience some difficulties in learning, so they need an individual approach and attention. It would be good if a sick child started studying in a special school for children with these difficulties. There are boarding schools, the program of which is adapted specifically for such a contingent.

If a sick child has brothers or sisters, they need to be given equal attention so that the children do not think that they are abandoned.

Duchenne myopathy is the most famous, striking and at the same time the most severe disease from the group of hereditary progressive myopathies. It is based on a hereditary defect in dystrophin, a protein that maintains the integrity of muscle fiber membranes. Depending on the degree of dystrophin deficiency, myopathies of varying severity occur, of which the most severe is Duchenne myopathy (complete absence of dystrophin), and the most common is Becker myopathy (some amount of dystrophin is retained).

The disease is inherited recessively, linked to the X chromosome, so boys are affected. Women who are carriers of the gene do not get sick, but some of them have increased CPK activity or mild muscle weakness. In most patients, weakness becomes noticeable before the age of three: they often fall, have difficulty getting up, and gradually lose acquired motor skills.

One of the early symptoms is the staircase symptom: to get up from the floor, the child gets on all fours and then slowly straightens up, resting his hands first on his knees and then on his hips. A waddling gait is characteristic. Most patients have pseudohypertrophy of the calf muscles: they are thickened and feel hard and elastic to the touch. Weakness increases: by the age of 8-10, children walk with difficulty, and by the age of 12 they completely lose the ability to walk. At this time, joint contractures and scoliosis form, increasing as mobility decreases. The myocardium is often affected: already at an early stage of the disease, changes occur on the ECG and EchoCG, and at a later stage, heart failure is possible. Some patients have non-progressive mental retardation. Due to heart damage and steadily increasing weakness of skeletal muscles with inevitable impairment of respiratory function, patients die on average at the age of 20 years. The main causes of death are respiratory and heart failure.

Duchenne myopathy can be inherited from the carrier mother or result from a new mutation (in 30% of cases). Gene diagnostics makes it possible to detect characteristic mutations and thereby confirm the diagnosis of Duchenne myopathies in boys or carrier status of the gene in women in approximately 70% of cases. Direct prenatal gene diagnosis is possible in these families. In most other families, reliable prenatal gene diagnosis is also possible using other techniques (indirect prenatal gene diagnosis).

Another diagnostic method is the study of dystrophin in muscle tissue; With Duchenne myopathies, dystrophy is not detected. This method is reliable for confirming a clinical diagnosis, but it is not suitable for diagnosing gene carriage and for prenatal diagnosis.

An approximate preliminary method for diagnosing gene carriage in women is to determine the activity of K.PK (it is increased in approximately half of the carriers).

Help for patients mainly consists of exercise therapy (in particular, slowing down the formation of contractures), selection of auxiliary devices for movement (splints, canes, walkers) and surgical correction of contractures and scoliosis. Passive muscle stretching helps slow down the formation of contractures. Treatment with glucocorticoids (every other day) has become widespread, prolonging life by several years. Various other treatments have been proposed and tested, but none significantly improve the prognosis of this severe myopathy.