Clinical And Genetic Analysis Of 14 Pedigrees And Sporadic Cases In China Diagnosed To Hereditary Palmoplantar Keratoderma

BackgroundHereditary palmoplantar keratoderma(PPK)is a rare congenital disease characterized by excessive abnormal thickening and keratinization of the skins on palm and plantar,which is inherited in autosomal dominant or autosomal recessive pattern.According to whether it is accompanied by pathogenicity of other tissues and organs,it can be divided into isolated and non-sisolated palmoplantar keratoderma.Isolated palmoplantar keratoderma has only skin manifestations,which can be divided into four types:diffuse,punctate,focal and striated.Each type may include several subtypes,and the clinical classification is complex.Different subtypes have different pathogenic genes,and the diffuse type mainly includes KRT1,KRT9,SERPINB7,SLURP 1,etc;at present,there are only AAGAB and COL14A1 genes for punctate PPK;pathogenic genes of focal PPK include KRT16,KRT6c,etc;pathogenic genes of striated PPK include DSG1 and DSP.Gene detection is of great significance in determining the pathogenic mutations of palmoplantar keratoderma and assisting its clinical diagnosis and typing.ObjectivesTo determine the pathogenic genes and their clinical diagnosis and typing of 14 patients clinically diagnosed as palmoplantar keratoderma,including 8 pedigrees and 6 sporadic cases.Methods1.Case collection:We collected the patients clinically diagnosed to PPK and treated in the outpatient department of our hospital from 2000 to 2022,A total of 8 pedigrees and 6 sporadic cases were collected to obtain their clinical data and peripheral blood.2.DNA extraction and whole-exome sequencing:DNA was extracted from peripheral blood,and whole-exome sequencing was performed on probands from 8 pedigrees and 6 sporadic cases using IlluminaTM HiSeq 2000 sequencing platform to find their pathogenic mutations.3.Sanger sequencing:Sanger sequencing was carried out for mutations found in all pedigrees and sporadic cases to validate the authenticity of these mutations.4.Pathogenicity analysis of new mutation site:Use PolyPhen-2 and SIFT to predict the pathogenicity of mutation sites;Use dbSNP to predict the minimum allele frequency of mutation site.ResultsWe found 2 novel and 7 previously reported mutations in 7 pedigrees and 6 sporadic cases by whole-exome sequencing.These mutations were found in KRT9,SERPINB7,SLURP1,AAGAB,KRT16 and GJB2.No such mutation was found in a family and the mutation detection rate was 93%.Mutations in KRT9,SERPINB7 and SLURP1 were found in 6 pedigrees and 3 sporadic cases,and the clinical diagnosis was diffuse PPK.A novel and a reported mutation were identified in 2 sporadic cases diagnosed as focal PPK,and the novel one was predicted to be pathogenic by PolyPhen-2 and SIFT.In a family with clinical diagnosis of punctate PPK,we detected a novel frameshift mutation in AAGAB which was considered pathogenic after analysis.A sporadic patient with PPK and deafness was found to have a missense mutation in GJB2.ConclusionIn this study,the pathogenic mutations of 7 pedigrees and 6 sporadic cases of palmoplantar keratoderma were identified by whole-exome sequencing and Sanger sequencing,and they were clearly classified,and 2 novel mutation sites were found,which enriched the genetic spectrum of palmoplantar keratoderma.For one pedigree that had no such mutation,it indicated that there were unsolved genetic problems in palmoplantar keratoderma,which provided a theoretical basis for the study of the mechanism of palmoplantar keratoderma.