The distribution and frequency of the CFTR gene mutations vary considerably between countries and ethnic groups. Russians are an East Slavic ethnic groups are native to Eastern Europe. Russians, the most numerous people of the Russian Federation (RF), make about 80% of the population. The aim is to reveal the molecular causes of CF in ethnic Russian patients as comprehensively as possible. The analysis of most common CFTR mutations utilized for CF diagnosis in multiethnic RF population accounts for about 83% of all CF-causing mutations in 1384 ethnic Russian patients. Variants c.1521_1523delCTT (F508del), c.54-5940_273+10250del21kb (CFTRdele2,3), c.2012delT (2143delT), c.2052_2053insA (2184insA), and c.3691delT (3821delT) are most typical for CF patients of Russian origin. DNA of 154 CF patients, Russian by origin, in whom at least one mutant allele was not previously identified (164 CF alleles), was analyzed by Sanger sequencing followed by the multiplex ligase-dependent probe amplification (MLPA) method. In addition to the 29 variants identified during the previous test for common mutations, 91 pathogenic CFTR variants were also revealed: 29 missense, 19 nonsense, 14 frame shift in/del, 17 splicing, 1 in frame ins, and 11 copy number variations (CNV). Each of the 61 variants was revealed once, and 17 twice. Each of the variants c.1209G>C (E403D), c.2128A>T (K710X), c.3883delA (4015delA), and c.3884_3885insT (4016insT) were detected for three, c.1766+1G>A (1898+1G>A) and c.2834C>T (S945L) for four, c.1766+1G>C (1898+1G>C) and c.(743+1_744-1)_(1584+1_1585-1)dup (CFTRdup6b-10) for five, c.2353C>T (R785X) and c.4004T>C (L1335P) for six, c.3929G>A (W1310X) for seven, c.580-1G>T (712-1G>T for eight, and c.1240_1244delCAAAA (1365del5) for 11 unrelated patients. A comprehensive analysis of CFTR mutant alleles with sequencing followed by MLPA, allowed not only the identification of 163 of 164 unknown alleles in our patient sample, but also expansion of the mutation spectrum with novel and additional frequent variants for ethnic Russians.

Primary ciliary dyskinesia (PCD) is a rare hereditary disease from the group of ciliopathies, which is based on a defect in the cilia ultrastructure of the respiratory epithelium and similar structures (sperm flagella, villi of the fallopian tubes, ventricular ependyma, etc.), leading to motor function impairment. The prevalence of the disease varies significantly around the world and is not known reliably in the Russian Federation.The aim of the review was to analyze literature data on modern approaches to the diagnosis and treatment of PCD.Methodology. The data of 90 articles and the opinions of experts providing care to patients with PCD were used.Results. The classic manifestations of PCD depend on age. The leading manifestations of the disease in patients with PCD are recurrent inflammatory diseases of the upper and lower respiratory tract (bronchitis, pneumonia), with the formation of bronchiectasis, damage to the ENT organs (chronic rhinitis, rhinosinusitis, nasal polyposis, repeated otitis media, progressive hearing loss). Currently, there is no single method which could serve as a “gold” standard for diagnosing PCD. The diagnosis of PCD is based on the characteristic clinical picture in combination with the results of special tests (nitric oxide in exhaled air, DNA diagnostics, high-speed video microscopy, transmission electron microscopy). The genetic diagnostics has not been developed sufficiently in the global practice yet and is unavailable in our country. The approach to the treatment of a patient with PCD should be multidisciplinary due to multiple organ lesions. According to the European consensus, the goal of PCD therapy is to restore or maintain normal lung function. There have been no randomized trials of treatment for PCD, and therefore all treatment recommendations are based on very low-level evidence or extrapolated from cystic fibrosis guidelines. Recommendations on mucolytic, antibacterial and anti-inflammatory therapy of PCD are given with consideration for the international and domestic experience.Conclusion. The development of a new version of clinical guidelines containing up-to-date relevant information will improve the diagnosis and treatment of PCD in the Russian Federation.

In the cohort of Russian patients with cystic fibrosis, the p.[Leu467Phe;Phe508del] complex allele (legacy name [L467F;F508del]) of the CFTR gene is understudied. In this research, we present the results of frequency evaluation of the [L467F;F508del] complex allele in the Russian Federation among patients with a F508del/F508del genotype, its effect on the clinical course of cystic fibrosis, the intestinal epithelium ionic channel function, and the effectiveness of target therapy. The frequency of the [L467F;F508del] complex allele among patients with homozygous F508del was determined with multiplex ligase-dependent probe amplification followed by polymerase chain reaction and fragment analysis. The function of ionic channels, including the residual CFTR function, and the effectiveness of CFTR modulators was analyzed using intestinal current measurements on rectal biopsy samples and the forskolin-induced swelling assay on organoids. The results showed that the F508del/[L467F;F508del] genotype is present in 8.2% of all Russian patients with F508del in a homozygous state. The clinical course of the disease in patients with the F508del/[L467F;F508del] genotype is severe and does not vary from the course in the cohort with homozygous F508del, although the CFTR channel function is significantly lower. For patients with the F508del/[L467F;F508del] genotype, we can recommend targeted therapy using a combined ivacaftor + tezacaftor + elexacaftor medication.

The basic therapy of cystic fibrosis is currently aimed at slowing down the pathological processes associated with a decrease in the CFTR protein activity (cystic fibrosis transmembrane conductance regulator) in the gastrointestinal tract and the respiratory system. The pancreatic insufficiency is well compensated by replacement therapy with microsphere enzyme preparations and a high-calorie diet rich in proteins and fat. Chronic treatment of cystic fibrosis-related lung disease aims to improve the clearance of the bronchial tree, suppressing chronic bacterial infection and local chronic inflammation. However, no therapy was available to correct the defect in the gene or its product until 2012.The aim was to analyze literature on CFTR modulators, including their efficacy and safety, and assess the potential for developing new modulators to treat cystic fibrosis.Materials. The review included literature data (45 publications) on the use of CFTR modulators and international websites’ data.Results. Since the discovery of the CFTR gene in 1989, more than 2000 mutations or variants of the CFTR gene (hereinafter referred to as genetic variants) have been described. They interfere with the synthesis of the CFTR protein, its transport to the apical membrane of the cell, or disrupt its function as a channel for chloride anions. Although it is currently not possible to completely replace the mutant gene with a normal copy, small molecules have been identified that can modify the mutant CFTR protein and amend its function. The potential therapeutic measures are determined by class of the mutation. In clinical practice, pharmacological modeling of ion transport is currently possible only with the use of CFTR modulators: correctors and potentiators. The review defines these groups of drugs and describes 4 licensed CFTR modulators, including molecules of ivacaftor, lumacaftor, tezacaftor, elexacaftor. The data on the promising emerging next generation modulators and the prospects for the personalized selection of drugs using the assays on intestinal organoids are presented.

A registry of patients with cystic fibrosis (CF) of the Russian Federation has been compiled annually since 2011. Analysis of the national registry with large amounts of clinical and laboratory data helps understand changes in demographic indicators, plan measures to improve the quality of medical care and evaluate their effectiveness.Aim. To analyze health status of patients with cystic fibrosis in the Russian Federation and the dynamics of key clinical and laboratory parameters from 2011 to 2021. Methods. The health status of CF patients was assessed using the registry data from 2011 to 2021.Results. The analysis revealed an increase in the total number of patients from 1,026% in 2011 to 3,969 in 2021, in the number of patients identified by neonatal screening from 28.8% to 53.5%, and in coverage by genetic testing from 91.8 to 93.6%. At the same time, the number of mutations detected dropped from 80 to 90.5% and the number of patients with unidentified mutations decreased from 9.5 to 3.2%. The mean age at diagnosis of cystic fibrosis did not change (3.3 ± 5.5 in 2011 and 3.1 ± 6.2 in 2021) despite an increase in the number of patients diagnosed through neonatal screening. There was a difference in M ± SD age from 2011 to 2021 (11.5 ± 8.9 in 2011 and 14 ± 9.8 in 2021). The proportion of adult patients was 24.95% in 2011 and 27.4% in 2021. The therapy changed over 11 years - the number of courses of intravenous therapy decreased from 70.9 to 36.4%, the number of patients using inhaled antipseudomonal therapy expanded to 45%, the number of patients using hypertonic sodium chloride solution expanded from 8.7 to 70.7%, the use of glucocorticoids decreased. The targeted therapy was introduced in 2018, and the number of patients receiving pathogenetic drugs is growing.Conclusion. The observed changes are indicative of the health status of Russian patients with cystic fibrosis. Analysis of registries helps improve the organization of medical care, predict and implement sanitary and epidemic measures, plan therapy, and assist the regions in organizing outpatient monitoring and microbiological control. The registry is analyzed to organize health care for adult patients.