Introduction. Currently, sarcopenia, a disease characterized by a decrease in muscle mass, strength, and function, is increasingly being detected in clinical practice by physicians of various specialties. Sarcopenia is most often diagnosed in elderly and senile individuals, but can also develop in middle-aged and young individuals as a result of various diseases. A number of studies demonstrate the association of sarcopenia with non-alcoholic fatty liver disease (NAFLD). To date, issues of diagnosis and treatment of sarcopenia in routine clinical practice in patients with NAFLD, as well as the impact of sarcopenia therapy on the prevention of complications and progression of NAFLD, remain unresolved. Methodology. The Scientific Society of Gastroenterologists of Russia (SSGR) brought together 12 experts in the field of studying sarcopenia and NAFLD to make reasoned statements and recommendations on the issue of «Sarcopenia in patients with non-alcoholic fatty liver disease: pathogenesis, diagnosis and treatment». An extended literature search of articles in English was conducted using the keywords - sarcopenia, classification of sarcopenia, phenotypes and pathogenesis of sarcopenia, modern diagnostic methods and potential non-drug (rational nutrition and physical activity) and therapeutic methods for correcting sarcopenia, non-alcoholic fatty liver disease in the following international databases: PubMed, Google Scholar, Web of Science, Embase, Cochrane Database, search for ongoing relevant studies - on the ClinicalTrials.gov website. An extended literature search was carried out in Russian in the databases: electronic resource «Clinical Guidelines Rubricator of the Ministry of Health of the Russian Federation», eLibrary, RusMed. According to the information received, the text is structured into separate chapters. Each chapter contains key provisions (expert opinion) on the relevant section and the currently available data concerning a particular section. The authors present tables, expert conclusions and a list of modern literature devoted to sarcopenia and its phenotypes. Results (by key provisions). The experts worked to identify the most significant issues on the given topic, formulated questions relevant to clinical practice and gave reasoned answers to them, presented as «provisions» for clinical practice with comments based on evidence-based medicine. The formulation of questions, recommendations and provisions is based on a critical analysis of medical literature in English and Russian language databases. The results of the expert work are directly related to the quality management of patients with sarcopenia and NAFLD, and the key provisions they formulated can be used in clinical practice. Conclusions. The document presented by the expert group «Sarcopenia in patients with non-alcoholic fatty liver disease: pathogenesis, diagnosis and treatment» is intended to help practicing physicians improve their knowledge of the problem of sarcopenia and learn how to diagnose the syndrome early in routine clinical practice, and not only in patients of older age groups, but also in young and middle-aged patients, in whom sarcopenia develops as a consequence of chronic diseases.

Ferritin is an iron metabolism protein involved in the storage and protection of iron ions from uncontrolled oxidation. Serum ferritin levels are used as a biomarker to assess iron homeostasis. However, iron storage is not ferritin’s only biological function. Ferritin is an important biomarker of acute and chronic inflammation, and ferritin levels above 500-1000 ng/mL can indicate inflammatory processes of various origins. Therefore, in patients with existing inflammation, interpreting serum ferritin levels becomes more complex. Hyperferritinemia (ferritin levels of 500 ng/mL and above) accompanies not only iron overload but also liver disease, insulin resistance, cardiovascular and cerebrovascular pathology, COVID-19 (characterized by multiple organ dysfunction), and certain hematological disorders (macrophage activation syndrome, hemophagocytic lymphohistiocytosis) and corresponds to a more severe course of these pathologies. The results of an analysis of 34,266 publications on ferritin, conducted using mathematical methods of topological data analysis, suggest that ferritin (which is also a marker of acute and chronic inflammation) should only be used in combination with other biomarkers (transferrin, hemoglobin, hepcidin, etc.) to assess iron homeostasis. Diagnostic criteria that include serum ferritin levels should take into account the patient’s comorbidity. Depending on the pathology, ferritin levels can vary by four orders of magnitude: from 10-20 ng/ml for iron deficiency anemia to 900,000 ng/ml in individual cases of hemophagocytic lymphohistiocytosis. Ferritin thresholds in the range of 1000-6000 ng/ml are typical for iron overload diseases, macrophage activation syndrome, hemophagocytic lymphohistiocytosis, and coagulation disorders; ferritin thresholds in the range of 500-1000 ng/ml are typical for leukemia, blood transfusions, COVID-19, and other viral infections. At the same time, for bacterial infections, liver and kidney diseases, diabetes mellitus, vascular and neurodegenerative pathologies, threshold values of ferritin in the range of 300-500 ng/ml are of diagnostic interest, which approximately correspond to the established reference intervals for ferritin for adults. Therapeutic strategies for liver disease and other pathologies should consider hyperferritinemia as an indicator of a more severe course of the disease, including due to cytolysis of various tissues in multiorgan pathology. There are no established drugs for the treatment of diseases complicated by hyperferritinemia. Basic and clinical research shows that drugs based on standardized human placental hydrolysates (HPH) can be effectively used in multiorgan pathology complicated by hyperferritinemia. The peptides contained in standardized HPH simultaneously help reduce chronic and excessive acute inflammation, normalize iron metabolism (including inhibiting the development of tissue hemosiderosis), and exhibit a regenerative effect on damaged organ parenchyma.

These guidelines were compiled by specialists from the National Society of Pediatric Gastroenterology, Hepatology and Nutrition (NSPGHAN) based on national guidelines for the diagnosis and treatment of celiac disease, the NSPGHAN guidelines for the diagnosis of celiac disease, the European Society of Paediatric Gastroenterology, Hepatology and Nutrition (ESPGHAN), the Society of Pediatric Gastroenterologists, Hepatologists and Nutritionists (SPGNH), and literature data. These guidelines were updated and revised based on new research published in recent years, consistent with scientific evidence in this field. These guidelines are applicable to medical practice within the framework of the Procedure for Providing Medical Care to the Population for Gastroenterological Diseases. These guidelines for the diagnosis and treatment of patients with celiac disease serve as a guide for practitioners involved in the diagnosis, management, and treatment of celiac disease.