This literature review provides a range of neurological and other organic causes of brachialgia. Features of pain syndrome in different medical conditions are described.

Introduction. With the advent of new drugs — analogues of mitochondrial metabolites, the widespread introduction into practice of research methods for assessing the function of mitochondria in patients with neurological pathology and other diseases becomes relevant.

Study aim. To determine the change in the intracellular activity of mitochondrial enzymes (succinate dehydrogenase, α -glycerophosphate dehydrogenase, glutamate dehydrogenase, lactate dehydrogenase) in case of neuromuscular diseases.

Materials and methods. We examined 74patients with neuromuscular diseases. The activity of 4 mitochondrial enzymes involved in carbohydrate metabolism (lactate dehydrogenase), amino acid metabolism (glutamate dehydrogenase), fatty acids (α -glycerophosphate dehydrogenase), and mitochondrial respiratory chain complex II (succinate dehydrogenase) was evaluated. For a cytochemical study of the activity of mitochondrial enzymes in peripheral blood lymphocytes, the method proposed by A.G.E. Pearse as modified by R.P. Narcissov.

Results. The greatest changes were revealed in cases with myotonic dystrophy: statistically significant decreases in the average activity value of all studied enzymes (р <0.05).In cases with hereditary motor-sensory neuropathy of type I the activity of succinate dehydrogenase and glutamate dehydrogenase is reduced (р <0.05), in cases with type II there are deviations in the activity indicators of mitochondrial enzymes, more pronounced compared with type I, but not statistically significant (p >0.05). In patients with myasthenia gravis, a decrease in the activity of α -glycerophosphate dehydrogenase and glutamate dehydrogenase (p <0.05) was noted. Average values of succinate dehydrogenase and lactate dehydrogenase activity indicators were also reduced (p >0.05). In cases with Landusi-Dejerine myopathy the activity of succinate dehydrogenase, α -glycerophosphate dehydrogenase and glutamate dehydrogenase were reduced, of which only for α -glycerophosphate    dehydrogenase p <0.05. In the analysis of each case in groups of patients with the studied pathology, it was shown that in addition to patients with myotonic dystrophy, in which all patients decreased the activity of succinate dehydrogenase, α -glycerophosphate dehydrogenase and glutamate dehydrogenase, in other cases, in some patients, the studied enzyme activity did not change.

Conclusion. There are methods for studying these metabolites in plasma. The activity of mitochondrial enzymes is also examined. In cases with neuromuscular diseases, there are violations of the mitochondria. Therefore, it is necessary to consider such patients as metabolic patients and prescribe metabolic, antioxidant therapy to them.

Leukoencephalopathy with brain stem and spinal cord involvement and elevated lactate on magnetic resonance spectroscopy is a progressive hereditary disease of the nervous system clinically characterized by pyramidal and cerebellar dysfunction, dorsal column signs and sometimes axonal neuropathy with specific neuroimaging signs of damage to the nervous system, detected by magnetic resonance imaging. This disease is caused by mutations in the DARS2 gene. The article presents an analysis of three clinical cases with the manifestation of neurological symptoms in adolescence. Clinical features and magnetic resonance imaging findings are discussed, difficulties of differential diagnosis with multiple sclerosis are presented. Genetic screening algorithms are proposed.

Limb-girdle muscle dystrophy 2Q is one of the rarest forms of plectinopathies and is represented by an isolated muscular dystrophic syndrome, according to two previously described literature reports. There are five forms of plectinopathies, including limb-girdle muscle dystrophy 2Q, are caused by mutations in the PLEC gene, the alternative splicing of which determines the synthesis of 9 isoforms of the plectin protein (1, 1a, 1b, 1c, 1d, 1e, 1f, 1g, 3) performing cytolinker function in the neuronal, epithelial and muscle tissue.

The article describes the family observation of three sick siblings with the limb-girdle muscle dystrophy 2Q phenotype due to the presence of a new homozygous mutation (NM_201378.3:c.58G>T, NP_958780.1:p.Glu20Ter) in the isoform 1f PLEC revealed by whole-exome sequencing. Clinical, electromyography, visualization and histopathological features of limb-girdle muscle dystrophy 2Q were analyzed in detail. The onset of clinical manifestations in all the described siblings was observed in early childhood with moderate weakness mainly in the pelvic girdle muscles and proximal lower limbs with minimal involvement of the muscles of the shoulder girdle. A distinctive aspect is the stagnation of the myodystrophic process until 20—21 years, followed by the progression and development of episodes of respiratory failure, as well as the formation of rigidity of the cervical, thoracic spine and moderate contracture of the Achilles tendons. Typical features are marked atrophy of paravertebral muscles with the formation of pterygoid scapula and the presence of hypertrophy m. gastrocnemius, m. quadriceps femoris, m. deltoideus and m. triceps brachii. Histopathological examination m. vastus lateralis revealed myodystrophic process without inflammatory infiltration, muscle fiber cytoskeleton disorganization resulted from the plectin loss.

Electrocardiography signs of the early repolarization syndrome, focal cardiosclerosis and sinus tachycardia are described. For the first time, involvement in the pathological process of pulmonary tissue in the form of noninfectious bronchiolitis, atelectasis, and the development of the myasthenic syndrome causing episodes of respiratory failure resulted in the death of two described siblings aged 29 and 31 years. Discussed pathogenetic role of PLEC 1f isoform in the development of described syndromes, expands understanding of rare nosology limb-girdle muscle dystrophy 2Q.

Clinical and genetic characteristics of 9patients with Nonaka myopathy (GNE-myopathy) from Russia are presented. As a result of exom sequencing, 11 different mutations were revealed in the GNE gene, 8 of which were described earlier, and 3 – Сys203Ser, Met263CysfsTer and deletion of the whole gene — were detected for the first time. The peculiarities of clinical manifestation of Russian patients with GNE-myopathy are described.

Introduction. Mitochondrial myopathy with thymidine kinase 2 deficiency and spinal muscular atrophy 5q (SMA-5q) are two potentially curable hereditary diseases with different levels of damage to the neuromuscular system and etiology. Early childhood forms have a similar phenotype and are difficult for differential diagnosis.

The aim of the study — the description of the clinical and paraclinical characteristics of the mitochondrial myopathy with TK2 deficiency and informing health care specialists about the possibility of optimizing differential diagnosis.

Materials and methods. This study involved patients with a previously excluded by molecular genetic method a spinal muscular atrophy 5q diagnosis. Clinical and paraclinical descriptions are presented for 5 patients from 3 families. In addition, 96 patient samples were obtained from the archive of the Research Center for Medical Genetics. The diagnosis based on the clinical and paraclinical features of the disease and the detection of mutations in TK2 gene by sequencing of the NGS panel or TK2 gene directly.

Results. Eight patients with mitochondrial myopathy with TK2 from 5 unrelated families have been diagnosed. Three of them have been found retrospectively by analyze of 96 spinal muscular atrophy 5q negative samples.

Conclusions. Clinical and molecular genetic characteristics of mitochondrial myopathy with TK2 are presented. The feasibility of differential diagnosis of this rare myopathy with other neuromuscular diseases, including such frequent as spinal muscular atrophy 5q, is shown. The study revealed four previously undescribed mutations in the TK2 gene (c.169G>A (p.Gly57Ser), c.310C>T (p.Arg104Cys), c.338T>A (p.Val113Glu), c.655T>C(p.Trp219Arg)).