Clinical Manifestation And Pathogenic Gene Analysis Of Inherited Nonsyndromic Ichthyoses

Background Inherited nonsyndromic ichthyosis is a congenital ichthyosis that is limited to the skin.According to its genetic mode,morphology and histology,the disease can be divided into common ichthyosis,keratinopathic ichthyosis,and autosomal recessive ichthyosis(ARCI).Annular epidermolytic ichthyosis(AEI)is a special type of keratinopathic ichthyosis,which is a rare autosomal dominant disease,AEI was recently described in ten separate families in the English literature.There are no reports on the phenotypic heterogeneity of AEI.AEI patients present blisters in the early stage and polycyclic psoriatic lesion in adults,which is caused by mutations in KRT1 or KRT10 genes,the mutation sites include p.I479 T and p.I479 F on KRT1 genes and p.I446 T and p.A156 P on KRT10 genes.Ichthyosis vulgaris(IV)is the most common type of nonsyndromic ichthyosis,in the Chinese population,the prevalence rate is reaching about 2.29%,IV is characterized by a fine brown scale over the exterior surface of the arms and legs.Mutations in the FLG gene encoding filaggrin are the main genetic susceptibility factors for IV and atopic manifestations.So far,more than 50 mutation sites have been reported.Lamellar ichthyosis(LI)is a mild form of autosomal recessive ichthyosis,which has been reported in genes including TGM1,ABCA12,ALOXE3,ALOX12 B,CERS3 and cytochrome P450,TGM1 and ABCA12 have been frequently reported.The clinical manifestations of nonsyndromic hereditary ichthyosis diseases are different,and the pathogenic genes are different,the traditional clinical diagnosis methods may have some limitations,and Genomic exon sequencing technology can detect the variation of gene structure,so Whole-genome sequencing(WES)technology has a broad application prospect to screen the pathogenic gene mutations and diagnose.Basing on complex clinical phenotypes and genetic heterogeneity of hereditary non-syndromic ichthyosis,WES is an important research method and diagnostic method at present.Object In view of the proband's clinical manifestation and previous genetic research,WES and Sanger sequencing was performed with a group of nonsyndromic ichthyosis families,which enrichs the gene mutation database and provides academic support for subsequent genetic diagnosis on nonsyndrome ichthyosis.Methods(1)Samples with clinically diagnosed of ichthyosis vulgaris in five families and suspected annular epidermolytic ichthyosis in a family and suspected lamellar ichthyosis in a family are selected from clinics or the biobank of the Institute of Anhui Medical University.(2)In the seven families,the affected individuals were selected to conduct WES,by WES technology,the original data is obtained through a series of steps such as purification,capture and sequencing,and the original sequence data is analyzed.The harmful mutation sites or genes related to diseases are screened out through quality assessment,mutation site classification and other steps and a list of suspected mutations were obtained.Analyses of the reported causative genes(KRT1,KRT10,FLG and TGM1)were emphasized.(3)The suspected pathogenic mutations were verified by Sanger sequencing in the samples of seven families to study genotype-phenotype co-segregation.Results(1)A compound heterozygous mutation(NM?006121),c.1436T>C(p.I479T))located on exon 7 of the KRT1 gene was found in the AEI family,The results combined with clinical manifestations and skin imaging,pathological diagnosis and immunohistochemical detection,the diagnosis of AEI in the proband is clear.(2)By the analysis of 5 families of IV,FLG mutations were studied,and 5 known pathogenic mutations were found in the families,which were c.3321 del A(p.S1107fs),c.12064A>T(p.K4022X),c.4544C>A(p.S1515X),c.4420C>T(p.R1474X),c.2476C>T(p.R826X).And 1 unreported mutation was found in the family,which was c.11227C>T(p.R3743X).(3)Mutations of the known TGM1 gene,c.424C>T(p.R142C)were detected in the LI family.Combined with clinical manifestations,the diagnosis of LI was accurate.Conclusions(1)A heterogeneous AEI family with phenotypic heterogeneity was reported for the first time in the world,enriching in the mutation spectrum of cyclic epidermolytic ichthyosis.(2)The analysis of 5 IV families enriched the study on FLG gene mutations of IV.And one novel mutation were discovered in this study,which will enrich the mutation spectrum of IV.(3)We also report a case of LI of Tibetan,which made a clear diagnosis and enriched the understanding of TGM1.(4)The combination of WES and Sanger sequencing is one economic and efficient way on nonsyndromic ichthyoses.The mutation analyses can offer an academicl foundation for the further prenatal screening and timely therapeutic management.