Analysis Of Clinical Characteristics And Mutation Of Pathogenic Gene In One Netherton Syndrome Family

BackgroundHereditary ichthyosis is a group of genetic diseases characterized by generalized dryness,desquamation,and hyperkeratosis due to mutations in genes primarily involved in skin barrier formation.Netherton syndrome(NS,OMIM #256500)is a rare autosomal recessive inherited congenital keratosis disorder classified as a syndromic hereditary ichthyosis.The typical clinical feature of Netherton syndrome is a triad of congenital ichthyosiform erythroderma(CIE)or ichthyosis linearis circumflexa(ILC),trichorrhexis invaginata(TI),and atopic predisposition.Netherton syndrome is caused by a loss-of-function mutation of SPINK5(serine protease inhibitor of Kazal type 5)on chromosome 5q31-32 that encodes a lymphoepithelial Kazal-type related inhibitor(LEKTI).Whole exome sequencing(WES)allows for the study of genetic mutations in functional regions of encoded proteins by using sequence capture technology to capture DNA from genome-wide exonic regions and enriching it for genomic analysis using High-throughput sequencing.Whole exome sequencing has become one of the most frequently used DNA sequencing methods due to its high efficiency,economical and accurate technical features.ObjectivesTo investigate the clinical features and molecular genetic pathogenesis of a Netherton syndrome family and the genotype-clinical phenotype correlation in patients with Netherton syndrome.Methods1.Detailed history and physical examination were performed for all patients in a Netherton syndrome family,and blood samples were collected for genetic analysis and serum Ig E level detection.Scalp hairs and skin samples were collected for scanning electron microscopy,histopathology and immunohistochemical examination.2.First,Sanger sequencing was used to detect the mutation of KRT1,KRT10 and KRT2 gene in this family.If none of pathogenic mutation is detected,WES is performed to obtain the raw data through a series of steps such as DNA interruption,purification,hybridization and capture,sequencing,and the quality assessment and data analysis of the raw data are conducted.The relevant mutation sites were screened by ANNOVAR analysis software.Finally,Sanger sequencing was used to verify the screening mutation by sequencing an expanded sample size in the family members and healthy controls.3.We searched and summarized literature related to Netherton syndrome in PUBMED and CNKI database in the last 10 years to explore the relationship between the pathogenic mutations of SPINK5 gene and clinical features of Netherton syndrome.Results1.The clinical manifestations of the proband were congenital ichthyosis erythroderma with scattered flaccid blisters.The hair color was yellowish,lusterless,and easy to pull out.The laboratory examination of serum Ig E level is significantly elevated.Trichoscopy examination showed sign of TI in only a few scalp hairs.The staining intensity of LEKTI protein in the skin tissue of the proband was significantly lower than that in normal skin tissue.2.A novel homozygous frameshift mutation c.2474＿2475del(p.Glu825Glyfs*2)in exon 26 of SPINK5 gene was identified in the proband after integrative analysis.His parents and his younger brother were the heterozygous carriers of this mutation.The diagnosis of NS was definitely made for this patient.3.The study of correlation between genotypes and clinical phenotypes showed that the clinical phenotype of NS is heterogeneous.The N-terminal mutations of LEKTI cause a severer phenotype,while the C-terminal mutations of LEKT1 are related to a milder phenotype.Conclusions1.The genetic testing clarified the clinical diagnosis of NS,and identified a novel pathogenic mutation of SPINK5 gene,so elucidated the molecular genetic pathogenesis of this NS family.Our study further expanded the reservoir of SPINK5 mutations in NS.2.There was some correlation between the genotype and clinical phenotype in NS.