Geno-phenotypic features of cystic fibrosis in Russian children from the Chechen and Karachay-Cherkess Republics

Background: Cystic fibrosis (CF) is an autosomal recessive disease that occurs with a frequency of 1:1,500 to 1:5,000 newborns, according to the World Health Organization. In the Russian Federation, the average incidence of the disease is 1:10,000 newborns. The medical and social significance of this disease is associated with the early disability of patients, the need for long-term treatment and constant follow-up, as well as the heterogeneity of phenotypic manifestations, which in turn requires early diagnosis using molecular genetic methods. The aim of the study: To study the clinical and molecular genetic characteristics of children with CF from the Chechen and Karachay-Cherkess Republics. Materials and methods: The study included 237 patients with a confirmed diagnosis of CF. Molecular genetic diagnostics was performed using the method of mass parallel sequencing using a hybridization target panel that includes the entire CFTR gene. Sequencing was performed on the MiSeq platform. All causal nucleotide variants were validated using Sanger sequencing. Results: The most common amino acid variants of the CFTR gene in patients with CF from the Chechen Republic are: p.Y515* (94 alleles/78.3%), p.E92K (18 alleles/15%). The presence of variants p.Y515* and p.E92K in the heterozygous state in the genotype is more often a favorable prognostic factor for the absence of pancreatic lesion. The main distinctive clinical feature of these patients is the onset of the disease with manifestations of pseudo-Bartter syndrome. The major amino acid variant of the CFTR gene in patients with CF from the Karachay-Cherkess Republic is: p.W1282* (28 alleles/70%). The number of patients with pseudo-Bartter syndrome was 54.5%. In 90% of cases, in patients who are homo- and heterozygous according to p.W1282*, a severe degree of pancreatic insufficiency was noted. Conclusion: Patients with cystic fibrosis from the Chechen and Karachay-Cherkess Republics are a difficult category of patients, despite neonatal screening, and cystic fibrosis therapy developed and implemented. This is partly due to the peculiarities of the phenotype and the unique distribution of alleles and genotypes of the CFTR gene. The high number of homozygous variants of the CFTR gene in patients from the Chechen and Karachay-Cherkess Republics is probably due to monoethnic marital assortativity.