The successes of biology, biochemistry, and physics have made it possible to expand the possibilities of the pathogenetic study of various neuromuscular diseases. The widespread introduction of histochemical techniques and electron microscopy has helped to identify a number of new diseases and decipher the group of myopathies with characteristic structural changes. They mainly represent peculiar defects in the development of muscle tissue and constitute a group of non-progressive myopathies.
Disease described in 1966 for the first time, the Spiro with colleagues . It got its name from the term ” myotubule ” – immature embryonic muscle cell. This form of myopathy is characterized by generalized muscle weakness with malnutrition and tendon areflexion and is detected from the moment of birth. Often the oculomotor muscles suffer – patients have a slight ptosis, limitation of eye movements. Weakness of facial muscles is noted. Bone deformities, in particular scoliosis, may occur. EMG reveals a muscle type of change.
An atomorphological study reveals a decrease in the size of muscle fibers, the nuclei in them are located in the center and are surrounded by a zone devoid of myofibrils. Such a picture served as the basis for the name of the disease, “ centronuclear myopathy”.
Sporadic forms are more commonly observed, although familial cases are known . The type of inheritance is not exactly set.
Non-raspberry myopathy. This form of the disease has been known since 1963, after describing Shy with colleagues . Symptoms are detected from the moment of birth or in the first 1-2 years of life. There are moderate weight loss and muscle weakness in the arms and legs, facial muscle weakness, and tendon areflexia. Along with muscle pathology, bone abnormalities are often observed: high palate, long face, chest deformity, scoliosis, hollow feet. Intelligence is usually saved.
The course of the disease is usually stationary, but cases with rapid progression of muscle weakness and death have been described. EMG reveals changes characteristic of the muscle level of the lesion. The activity of serum enzymes is normal or slightly increased. Specific changes are found in the study of muscle biopsy. When stained according to Gomori, peculiar filamentous structures that are colored in red are found in muscle fibers.
Inheritance of the disease in an autosomal dominant and autosomal recessive manner.
Central stem disease
The disease was described in 1956 by Shy and Magee , it belongs to congenital forms and is manifested by muscle weakness and hypotension mainly in the proximal limbs, especially in the legs. Hypotrophy is mild, tendon reflexes; saved. Sick children have a certain delay in motor functions, they later begin to walk, but in the future there is some compensation, patients fully service themselves and can even perform one or another job. Intelligence fully preserved.
The essence of the disease consists in the formation in the center of the muscle fiber of an amorphous region with a bunch of abnormal “myofibrils” stained blue according to Gomori . An electron microscopic examination reveals the absence of mitochondria and the sarcoplasmic reticulum in the region of these structures , a sharp decrease in interfibrillar spaces and a change in the configuration of z-bands. Type I fibers suffer. The type of inheritance is autosomal dominant.
In 1966, Shy with colleagues . described two types of mitochondrial pathology in non-progressive myopathy syndrome : megaconial myopathy, where the mitochondrial abnormality consists in a sharp increase in their size (1000 or more times compared with the norm) and pleoconial myopathy, accompanied by an increase in the number of mitochondria in muscle cells. Clinically, the disease is manifested by muscle weakness, decreased tone and hypotrophy mainly in the proximal limbs, but in some cases muscle weakness is observed in the shoulder- facial region or is generalized . The disease may be accompanied by painful muscle cramps. The first symptoms are detected from the moment of birth or in the first decade of life, the process, as a rule, does not progress. Along with changes in the structure of mitochondria, a pathomorphological study can reveal excess fat in muscle fibers, in the liver, and kidneys. Anomaly mitochondria sometimes seen in other diseases, such as Duchenne muscular dystrophy , periodic paralysis, illness macro- Hardelot , with ocular myopathy.
Myopathy with hypermetabolism
Myopathy with hypermetabolism due to increased breathing of mitochondria (Luft disease). In 1962, Luft described a patient who had symptoms resembling thyrotoxicosis (fever, excessive sweating, polydipsia, polyphagia, tachycardia, weight loss), as well as myopathic syndrome in the form of moderate muscle hypotrophy, lack of tendon reflexes, creatinuria and changes on EMG on myogenic type. The main metabolism in the patient ranged from +144 to + 213% compared with the norm. Thyrotoxicosis was excluded, and by biopsy, accumulations of mitochondria were found in all muscles, many of which were gigantic. Subsequent studies gave reason to believe that with Luft disease, there is a primary pathology of muscle mitochondria, which leads to the separation of respiration and phosphorylation with the release of a large amount of heat. Along with an increase in body temperature in these patients, heat intolerance is observed.