Congenital myopathies
Congenital myopathies are a broad concept of neuromuscular disorders, a group of rare primary muscle defects that are inherited, cause hypotension at birth or during the newborn period. Diseases belonging to the group of congenital myopathies have a complex clinical picture and similar symptoms, which significantly complicates their diagnosis and treatment.
The content of the article:
Classification of congenital myopathy
Symptoms of congenital myopathy
Characteristics of certain types of congenital myopathy
Diagnosis of congenital myopathy
Treatment of congenital myopathy
Congenital myopathies
It manifests itself as diffuse muscle weakness and a decrease in muscle tone, the severity of which directly depends on the type of myopathy and the level of its complexity. In severe cases, it can lead to death from respiratory failure.
Congenital myopathy is a genetically determined disease. Different types of myopathy can be located at different chromosome loci, so they can be inherited recessive, dominant or together with the X chromosome. Genetic pathology disrupts the synthesis of protein, which is part of muscle tissue, which leads to a violation of the structure of muscle fibers. As a result, the muscles lose the ability to contract normally, muscle weakness is observed.
Congenital myopathy usually manifests itself in early childhood (very rarely manifests itself in adults) and retains its symptoms throughout the patient’s life. More often than not, the disease progresses slightly or does not progress at all.
The pathogenesis of myopathy has not been fully studied and the causes of its occurrence have not been clarified. There is a hypothesis of a “membrane defect” of muscle cells and cytoplasmic organelles, which many neurologists call the cause of the origin of the disease.
Classification of congenital myopathy
Muscle biopsy provides certain biochemical and morphological data, on the basis of which all diseases of congenital myopathy can be conditionally divided into two large groups.
Congenital muscular dystrophy
The first group is congenital muscular dystrophy (a violation of the function and structure of muscle fibers as a result of a failure of the synthesis of proteins that are part of them). There is no clear classification of congenital muscular dystrophy, but based on the hypotheses of the pathogenesis of this group of the disease, two groups can be distinguished:
merosin is a negative disease characterized by a deficiency or absence of the mesonin protein, which is part of the striated muscles;
congenital structural myopathies and merosin-positive, in which the concentration of mesonin is normal.
Merosin-negative group of diseases is divided into several types:
congenital muscular dystrophy of Fukuyama;
muscle-eye-brain syndrome;
Walker-Warburg syndrome.
The clinical picture of the diseases of the merosin-negative group is very similar to the symptoms of classical congenital myopathies, but a distinctive feature is the involvement of various brain structures in the general symptoms, which leads to further mental retardation, developmental delay. Diseases of the merosin-positive group are much less likely to include damage to the central nervous system (approximately 10% of patients have brain damage) and usually does not entail inhibition of intelligence. The clinical picture is characterized by spinal deformity and violation of facial features.
Congenital structural myopathies
The second group is congenital structural myopathies (violations of the integrity of the cytoskeleton of muscle fibers and the occurrence of pathology in the muscle biopsy). This group of diseases is characterized by a violation of the synthesis of proteins responsible for growth and other functions of muscle formation in the early development of the embryo.
Congenital structural myopathies include:
central core disease;
nonmaline myopathy;
centronuclear myopathy;
megaconial myopathy;
myopathy with a disproportion of muscle fiber types;
myopathy with multiple central rods;
myotubular myopathy;
myopathy with crystalline inclusions.
The clinical pictures of each of the diseases of this group are similar to each other and are characterized by muscle hypotension and hypertrophy, decreased reflexivity in the tendons and an increase in the concentration of creatine phosphokinase in the blood. There is a slow progression.
Symptoms of congenital myopathy
Congenital myopathy debuts most often in the first months of a child’s life. These diseases are characterized by the presence of the “sluggish child” syndrome: a noticeable decrease in muscle tone, weakness in the muscles, poor musculature development and exhaustion during the sucking process. With the development of the child, muscle weakness is more pronounced — lack of strength to stand on his feet or just lift his body, difficulties may arise when walking or sitting, there is a noticeable lag in physical development compared to other children of the same age.
Weakness in the muscles can be expressed strongly or slightly. Most often, the symptoms persist for the entire period of the patient’s life and practically do not progress or develop poorly. In some cases, it is possible to observe the inability to move independently, so the patient is forced to use a wheelchair, but the self-service skills acquired by him are not lost.
Congenital myopathies provoke not only the weakness of the muscles of the limbs and back, but also the muscles of the respiratory musculature, which is especially dangerous for infants. If the muscular weakness of the respiratory tract is expressed to a small extent, then the development of respiratory failure is observed. This, in turn, provokes various diseases of the respiratory tract (bronchitis, all kinds of pneumonia). Sometimes respiratory failure leads to death even in infancy. There are cases when muscle weakness decreases with age or vice versa progresses.
In some cases, congenital myopathy also manifests itself in the form of dysmorphic facial features (elongated skull shape, high palate) or pathologies of skeletal development (scoliosis, clubfoot, congenital hip dislocation, kyphosis).
Characteristics of certain types of congenital myopathy
Central core disease
It is inherited in an autosomal dominant way with incomplete penetrance (but there are also sporadic cases of heredity). This form of congenital myopathy is characterized by pathology of the proximal muscles of the extremities, but patients are able to acquire some motor skills. In infancy, there is a delay in motor development and hypotension, but this disease can be diagnosed only at a later age with changes in the skeleton and pronounced muscle weakness. At the same time, skeletal pathologies are observed: deformity of the feet, kyphoscoliosis, dislocation of the hips, shoemaker’s chest.
Most often, patients have a fragile figure and short stature. When diagnosing the disease, a muscle biopsy is performed, which shows the presence of multiple or single intermittent zones that are devoid of oxidation enzymes in some muscle fibers. Conducting other laboratory tests may show the norm. Patients with central core disease are prone to developing malignant hyperthermia.
Nemaline myopathy
The second name of this disease is congenital non—progressive filamentous myopathy. Heredity is mainly transmitted by autosomal dominant type, but recessive and sporadic also occur. Possible fatal outcome due to respiratory failure in early infancy. There are pronounced skeletal pathologies. The development of the disease may occur to one degree or another, or it may not progress at all. In some cases, patients are forced to move with the help of a sitting wheelchair, in others they suffer from respiratory failure. When diagnosing, a histological examination is carried out, which reveals inappropriate or rod-like crimson corpuscles in the muscles. EMG usually confirms the diagnosis of myopathy.
Myotubular myopathy
This type of congenital myopathy is inherited by an autosomal recessive type. Myotubular myopathy is characterized by the presence of centrally located nuclei in most muscle fibers. This resembles the appearance of a muscle on the myotubular intrauterine development of the fetus. As a result, the disease got its name.
Diagnosis of congenital myopathy
Diagnosis of congenital myopathies is a complex process, since a doctor needs to differentiate and determine a specific type of myopathy in order to prescribe adequate treatment and make a correct diagnosis. A neuropathologist identifies neurological symptoms, conducts electrophysiological and biochemical studies to establish the heterozygous carrier of the myopathic gene. Electromyographic examination using cutaneous electrodes often shows a decrease in the voltage of the EMG curve. In the biochemical analysis of blood in the serum, an increased concentration of aldolase and creatine kinase is observed.
Treatment of congenital myopathy
Treatment of congenital myopathy is ineffective. There is no clear treatment at the moment. Scientists are still arguing about whether it is possible to treat congenital myopathy. Medical institutes in different countries conduct research at the gene level — using stem cells. There is a symptomatic treatment, which consists in influencing the metabolic processes in the patient’s body, in particular, protein synthesis, an attempt to normalize the functions of the autonomic nervous system. Most often, drug treatment involves taking anabolic hormones (nerobol, ceraxone, retabolil, somazine), ATP. Vitamin therapy is mandatory. Anticholinesterase drugs are also prescribed.
A mandatory part of the treatment of congenital myopathies is physical therapy. It can be classes in the water or a set of exercises. Physical therapy is monitored by a trainer or a neurologist. In some cases, orthopedic correction is effective (for example, wearing orthopedic shoes, corsets or using orthopedic mattresses, pillows, chairs).
The condition and clinical picture of the disease is controlled by a neurologist, therapist, pediatrician, cardiologist and orthopedic traumatologist.
