Cystic fibrosis phenotype with the complex allele s466x-r1070q in Russian Federation Elena I. Kondrat'eva1

The aim of this study was to investigate phenotypic features of cystic fibrosis (CF) in patients carrying the complex allele S466X(TGA)-R1070Q. Methods. Data from CF register of Russian Federation, 2014, were used. The Russian CF register includes data of 2,131 patients from 74 regions of Russian Federation. The complex allele S466X(TGA)-R1070Q was found in 17 patients (the study group) and homozygous F508del mutation was found in 170 patients (the control group). The groups did not differ in main clinical, functional and microbiological parameters. Survival was also investigated. Results. Sweat chloride concentration was higher in the study group patients compared to the control group (116.53 mmol/L vs 102.2 mmol/L; р = 0.0341). There were 11.77% of deaths in a combined group of patients with the complex allele vs 3.53% in homozygous F508del mutation group (р = 0.159). Moreover, no significant difference in survival was found between the groups (p = 0.058). FEV1 was higher in the study group (84.69 ± 17.85%pred. vs 64.95 ± 27.16%pred. in the control group: р = 0.0483). Patients did not differ significantly in percentiles of height, weight, and body mass index. Amyloidosis and pneumothorax were seen in the control group, but not in patients with the complex allele S466X(TGA)-R1070Q. Polyps were diagnosed in 19 (11.17%) of patients with F508del/F508del genotype and were not found in the study group patients. Prevalence of diabetes mellitus and hepatic cirrhosis was similar in both the groups. Osteoporosis was diagnosed in 10% of control patients and in one (5.88%) of the study group patients. Chronic or intermitted Pseudomonas aeruginosa infection and chronic infection of Staphylococcus aureus were equally seen in both the groups, but Burkholderia cepacia сomplex and Stenotrophomonas maltophilia were found more often in the study group patients compared to controls (23.52% vs 10.58% and 11.76% vs 2.35%, respectively). Conclusion. The results of this study confirmed that the complex allele S466X(TGA)-R1070Q has properties of class I mutation and should be considered as a “severe” mutation.

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