What is Duchenne Muscular Dystrophy (DMD) Disease?
Duchenne Muscular Dystrophy (DMD) is a genetically based muscle disease. In Turkey, DMD disease accounts for approximately half of all neuromuscular disease cases. DMD disease is chronic and becomes increasingly severe over time. The quality of life of DMD patients can be improved by diagnosing them at an early stage and providing them with nutrition, physical therapy and special education. So what does DMD mean? What causes DMD and is there a cure? You can find the answers to all these questions in the following sections of the article.
What is DMD Disease?
DMD disease is a disorder that causes muscle degeneration and weakening due to changes in the dystrophin protein found in the muscle structure.
There are many proteins with different functions in the muscle structure. These proteins play a role in many different functions, from the location of the muscle to its functions such as contraction and relaxation. Dystrophin protein is one of the proteins located in muscle. Dystrophin protein connects the intracellular skeletal structure in the muscle cell to molecules outside the cell. Thus, it increases the strength of the muscle cell. If the dystrophin protein is low in quantity or defective in structure, muscle diseases called dystrophinopathy occur. In these diseases, the muscle becomes weak over time and loses its stiffness. Duchenne muscular dystrophy is the most common disorder among the dystrophinopathy group of diseases. Other diseases in this group; Becker Muscular Dystrophy (BMD), which is the milder form of DMD disease, is an intermediate group with clinical features between DMD and BMD, DMD-associated dilated cardiomyopathy.
What are the symptoms of DMD disease?
DMD disease occurs almost exclusively in men. Although rare, girls affected by this disease have been reported in the literature. DMD disease shows symptoms in the early stages of childhood. The average age of onset of symptoms is 2-3 years. In BMD, which is the milder form of DMD, symptoms may not appear until adolescence. DMD disease first affects the proximal muscles (arms, upper legs) that are close to the body. The muscles in the lower limbs are generally more affected than those in the upper limbs. Symptoms seen in children in the early stages of DMD, with the lower limbs being affected, are as follows:
- Difficulty walking, climbing stairs, jumping
- Loss of ability to walk
- Enlargement of calf muscles
- Lack of motor skill development
- Tiredness
- Sudden onset, rapid deterioration in neck, arm, leg and hip muscles
- learning disability
Muscle weakness in DMD patients continues to progress. For this reason, after the proximal muscles, distal parts such as forearm, hand and lower leg muscles, which are farther from the body, also begin to be affected. In order to compensate for the weakness in the muscles, DMD patients develop a posture in which the lumbar arch moves forward more than normal, called lumbar lordosis. In the later stages of DMD, weakness in the respiratory muscles also develops. This stage is the stage where the most serious complications of DMD disease occur, and patients may have difficulty surviving without respiratory support at this stage.
What Causes DMD?
DMD disease was first described by French neurologist Guillaume Benjamin Amand Duchenne in the 1860s. However, it was not until the 1980s that information about the disease increased. Researchers determined in 1986 that a mutated gene on the X chromosome leads to the development of DMD. The product of this gene, discovered a year later, was named dystrophin, and it was revealed that this protein was changed in DMD patients.
DMD disease is inherited in an X-linked recessive manner. The X chromosome is one of the sex chromosomes in humans. While the genetic structure of women is 46, XX, that of men is 46, XY. Therefore, while women have two X chromosomes, men have only one X chromosome. The development of DMD disease depends on the mutation of the dystrophin gene located on the X chromosome. In order for the disease to occur in women, there must be a mutant gene on both X chromosomes. However, in men, the mutation of the dystrophin gene on a single X chromosome is sufficient for the disease to occur. Therefore, the disease is mostly seen in men. Women with a single mutant X chromosome are carriers and have a chance of having a son with DMD.
Can DMD be treated?
DMD muscle disease is usually noticed by the family when the child’s walking deteriorates or the child loses previously acquired motor skills. When consulting a doctor, the child is given a detailed motor examination. In children with DMD, motor examination may reveal features such as lack of coordination and lagging motor skills according to age. To make a definitive diagnosis of DMD, first a blood test is performed. This test looks at the levels of an enzyme called creatine kinase. This enzyme leaks from the cells and mixes with the blood in cases where the muscle is damaged, and therefore its level is high in muscle diseases. High creatine kinase value alone is not sufficient for the diagnosis of DMD. This level may also increase in other muscle diseases. Therefore, if the patient’s creatine kinase level is high and the clinical picture is compatible with DMD disease, further examinations such as muscle biopsy and genetic testing are performed.
In the sample taken by muscle biopsy, histochemical examinations are performed to check whether there is dystrophin protein. Genetic testing examines whether there is any mutation in the patient’s dystrophin gene that could lead to DMD. According to the results of these tests, the patient can be diagnosed with DMD. There is no proven treatment for Duchenne Muscular Dystrophy. However, experts are working on various gene therapy applications for the mutant gene in the development of the disease. The basic approach in the treatment of DMD is the late emergence of complications that may occur due to the disease or the correction of already developed complications.
Due to progressive muscle weakness in DMD, children completely lose their ability to walk around the age of 12 and have to use a wheelchair. In order to enable patients to walk independently for longer periods of time, starting muscle exercises at an early stage helps the muscles to be in the best shape possible. Steroid treatment also helps muscle function to remain at a high level for a longer period of time. As a result of the weakening of the respiratory muscles, patients may experience complaints such as pneumonia and respiratory distress. Devices that provide respiratory support can be used in patients with severe respiratory difficulties. Muscle weakness that develops in the disease can also affect the heart. For this reason, children diagnosed with DMD should go to the cardiology department for a check-up at least once a year until the age of 10. Again, since problems such as contracture development and scoliosis are common in DMD, DMD patients should also be followed by the orthopedic department.DMD patients generally do not need a special nutritional list. However, special care should be taken to ensure that DMD patients receive adequate amounts of vitamin D. It is important to monitor weight control and malnutrition in patients receiving steroid treatment for muscle function, taking into account physical inactivity. In DMD patients, inactivity and weakening of the abdominal muscles can lead to constipation. To prevent this situation, it would be beneficial to create a diet rich in fiber foods.
What is the life expectancy of DMD disease?
In the past years, DMD patients died before they reached their 20s. However, today, increasing knowledge about the disease and concern about complications that may develop due to the disease have extended this period. In patients who are well cared for and regularly checked, life expectancy can reach up to the 50s. In order to prolong life and improve the quality of life in DMD patients, hospital check-ups should be followed closely, physical therapy should be given importance, and a suitable living arrangement should be created for the patient at home.
Diagnosing DMD disease at an early stage means detecting muscle weakness in its initial stages. Patients who start both medical and physical therapy early maintain their muscle functions at optimal levels for a longer period of time. For this reason, children with problems such as muscle weakness and delay in acquiring motor skills should definitely be taken to a doctor.
