Study On The Gene Mutation Spectrum And Clinical Characteristics Of Patients With 17α-hydroxylase Deficienc

Context17α-hydroxylase/17,20-lyase deficiency（17-OHD）is a rare type of congenital adrenal hyperplasia and accounts for nearly 1%of the condition.17-OHD has an estimated incidence rate of 1:50000 and is an autosomal recessive disorder caused by biallelic mutations in the CYP17A1 gene.The gene encodes the P450c17 protein composed of 508 amino acids,with activities of both 17α-hydroxylase and 17,20-lyase,which is a key enzyme in the biosynthesis of glucocorticoids and sex steroids.Different CYP17A1 genetic mutations can lead to varying degrees of loss of 17αhydroxylase/17,20-lyase.Accordingly,the patients suffered can be divided into combined 17α-hydroxylase/17,20-lyase deficiency and isolated 17,20 lyase deficiency（ILD）,the former can be further divided into complete or partial form of combined 17α-hydroxylase/17,20-lyase deficiency according to the quite different degrees of functional impairment of P450c17 protein.Low-renin hypertension,hypokalemia,female infantilism,primary amenorrhea,and male pseudohermaphroditism are the typical clinical features of 17-OHD.It has been reported that 88%of the 17OHD cases are not diagnosed accurately until puberty or even later due to its extremely low incidence and varied clinical phenotypes.Accordingly,some 17-OHD patients may develop HMOD because of poor blood pressure control and inappropriate disease management.For the patients of 17-OHD,early detection,accurate diagnosis and standardized treatment of 17-OHD are particularly important for the management of health status and the maintenance of long-term life quality.Due to the pretty high clinical heterogeneity of 17-OHD,the patients suffered often do not seek treatment owing to the lack of obvious clinical manifestations in the early stage and later consult the doctor for hypertension,hypokalemia and sexual development abnormality.The study of CYP17A1 genetic mutational profiles and clinical phenotype can provide important guidance for the clinical diagnosis and treatment of 17-OHD and help to better understand pathogenesis of 17-OHD from the perspective of molecular genetics,which is also of great significance for accurate molecular diagnosis and meaningful genetic counseling.Up to now,large sample studies of genetic mutational profiles and clinical characteristics on the 17-OHD patients are still lacking at home and abroad,the reported studies mainly focused on the clinical characteristics of 17-OHD patients at the first visit,the occurrence of HMOD and its related risk factors based on large clinical cohort has never been analyzed.ObjectiveThe purpose of this study was to explore the relationship between genetic mutations and the clinical features in a large cohort of 17-OHD patients in China,and the occurrence of HMOD and its related risk factors were also further analyzed.MethodsA total of 79 Chinese patients with 17-OHD who were admitted to the Peking Union Medical College Hospital（Beijing）were recruited for this retrospective cohort study between 2003 and 2021.Detailed medical data were collected and analyzed.DNA was extracted from peripheral blood leukocytes of patients,PCR amplification combined with Sanger sequencing was used to detect the CYP17A1 genetic mutations.The pathogenicity of the loci was annotated according to the American College of Medical Genetics and Genomics（ACMG）guidelines,and the relationship between the genotype and the clinical characteristics was also analyzed.68 patients with detailed damage assessment data of target organs（i.e.,heart,kidney and retina）were selected to analyze the occurrence of hypertension and HMOD,the Logistic regression model was further employed to analyze the risk factors of HMOD and the respective organ damage.Results1.37 kinds of genetic mutations（i.e.,point mutation,insertion mutation,deletion mutation and insertion/deletion mutation）were detected from 79 patients of 17OHD.Among them,27 mutations had been reported in previous literature.10 variants were newly identified in this study,including p.S94P,p.R96G,p.L361P,p.H373TfsX418,p.I394de1,p.H407QfsX415,p.L418X,p.W499X,c.436+1G>T and c.662₆66&c.666+7delTGAAGGTGAGATinsCCACCCTGCTTTCA.2 p.Y329KfsX418（57.0%,90/158）and p.D487_F489del（10.1%,16/158）were the top 2 mutations in this Chinese cohort.The mutations detected three times include c.297+2T>C,c.298-1G>A,R362H.The mutations detected twice include A82D,R96W,T101IfsX102,I259HfsX274,p.325/326/327Kdel,R358X,L361FfsX418,L361P,R362C,H373L and P409R.Exon 6 and exon 8 were the most common exons with pathogenic mutations,81.0%（128/158）of the total detected mutations were from the above two exons.p.Y329KfsX418 or p.D487 F489 del can be detected in 89.9%（71/79）%of the 17-OHD patients.3 Among the 68 patients with 17-OHD,3（4.4%）were normotensive and the remaining 65（95.6%）were hypertensive.36 patients（52.9%）were identified to have HMOD.Compared with the patients in the non-HMOD group,the patients in the HMOD group were older[26.00（24.00,30.00）years and 20.50（19.00,25.00）years,respectively].The hypertension duration of the 17-OHD patien ts in the HMOD was longer（8.50（2.50,12.00）years and 3.50（0.25,5.75）years,respectively）,and the hypertension grade（the proportion of grade 3,87.5%and 27.8%,respectively）and hypokalemia grade were both higher（the proportion of severe hypokalemia,56.3%and 16.7%,respectively）in the HMOD group.4 Disease duration,hypertension grade,and hypokalemia grade and medication duration were the independent risk factors for HMOD in the patients with 17-OHD,as inferred from multivariate logistic regression analysis.The risk of HMOD increased by 32%for each additional year of disease duration,10.2-fold for each one-grade increase in hypertension level,and 2.3-fold for each grade of exacerbation of hypokalemia.Conclusion1.In this study,37 variants（including 10 newly reported variants）were detected,which enriched the rare variation spectrum of CYP17A1 in 17-OHD.2.c.985₉87del TAC ins AA（p.Y329KfsX418）（57.0%,90/158）and c.1459₁467 del（p.del D487_F489）were ’hot spot’ mutations in Chinese 17-OHD patients.3.Patients with 17-OHD experience high incidence of HMOD4.There was no correlation between the HMOD occurrence and enzyme activity of mutant CYP17A1.Disease duration,hypertension grade,hypokalemia grade and medication duration are independent risks for the occurrence of HMOD.