【摘要】 目的 探讨1家系3例先天性厚甲症6b型患者的临床表型及致病基因突变情况。方法 收集1家系3例先天性厚甲症6b型患者的临床资料。采集该家系先证者、先证者姐姐及父母、100例健康对照者外周血，提取基因组DNA,采用高通量测序法检测皮肤病相关基因各外显子编码区域的序列突变情况，致病突变经PCR-Sanger测序验证。应用ClustalX2.1软件对比5个物种KRT6B基因编码蛋白在第172位氨基酸的保守性；应用PyMOL软件分析基因突变后对应蛋白结构的变化；应用Mutation Taster和PROVEAN预测KRT6B基因部分碱基缺失对蛋白功能的影响。结果先证者双足趾甲板呈蜡黄色程度不一的角化增厚，左足拇趾趾甲呈门槛样远端角化过度，右足底前端中央见甲盖大小淡黄色角化性斑块，边界清楚，摩擦后有水疱形成。先证者姐姐双足趾甲板角化增厚明显，呈黄褐色，伴拇趾侧缘甲盖大小角化斑块。先证者母亲双足拇趾趾甲受累较轻，余4趾趾甲呈黄褐色增厚，指甲板见棕褐色线状条纹；右足趾甲皮肤镜检查显示趾甲板横断面显著增厚，趾甲板与甲床间大量灰白色角质样物质，兼有明显横沟、纵嵴，可见黑色点状和线状结构。3例患者双手指甲板角化增厚程度较轻，毛发、口腔黏膜和牙齿均未见异常。基因测序结果显示，先证者、先证者姐姐及母亲KRT6B基因第1外显子发生c.516＿518delCAA(p.Asn172del)杂合突变，导致编码蛋白第172位缺失天冬酰胺；先证者父亲及100例健康对照者均未发现该突变。KRT6B基因编码蛋白在5个物种第172位氨基酸序列中完全保守，KRT6B基因c.516＿518delCAA突变位点对应蛋白结构发生变化，疑似为致病性突变。结合患者临床表现、家系特点与基因检测结果，最终诊断为先天性厚甲症6b型。结论 KRT6B基因c.516＿518delCAA(p.Asn172del)杂合突变可能是该家系先天性厚甲症6b型患者的致病原因。更多还原

【Abstract】 Objective To investigate the clinical phenotype and pathogenic gene mutations of 3 patients with pachyonychia congenita type 6b. Methods The clinical data of 3 patients with pachyonychia congenita type 6b were collected.The peripheral blood of the proband, his sister, his parents and 100 healthy controls were collected to extract genomic DNA, high-throughput sequencing was carried out to detect the sequence variation of the exon coding region of the skin disease related gene in the proband’s family, and the pathogenic variation was verified by PCR Sanger sequencing. ClustalX2.1 software was used to compare the conservation of amino acids at 172 positions of KRT6B gene coding proteins in 5 species. PyMOL software was used to analyze the changes of the corresponding protein structure after gene mutation. Mutation Taster and PROVEAN were used to predict the influence of partial base deletion of KRT6B gene on protein function. Results The nail plates of bipedal toes was keratinized and thickened in waxy yellow with varying degrees, and the left big toenail showed sill-like distal hyperkeratosis.There was a faint yellow keratotic plaque of the size of the nail cap in the center of the anterior of the right vola, with a clear boundary and blisters forming after friction.The nail plates of bipedal toes of proband’s sister had a pronounced hyperkeratosis and thickening and was yellowish-brown, with keratotic plaque of the size of the nail cap in the lateral border of the hallex. The proband’s mother had mild involvement of the great toenails, the remaining four toenails were yellow-brown thickened, and brown linear stripes were seen on the nail plates.Dermoscopy of the right toenail of the probands mother showed significant thickening of the cross-section of the deck,a large amount of gray-white keratinous material between the deck and the nail bed,with obvious transverse grooves and longitudinal crests,and the black dotted and linear structures were visible.In 3patients,the keratosis of both fingers was mild.There were no abnormalities in hair,oral mucosa and dental examination.Gene sequencing results showed that exon 1 of the KRT6B gene of the proband,his sister and his mother carried c.516＿518delCAA heterozygous mutation,resulting in the deletion of asparagine at the 172th position of the encoded protein,which was not found in his father and 100healthy controls.The protein encoded by KRT6B was fully conserved in the amino acid sequence at position 172in 5species,the corresponding protein structure of the c.516＿518delCAA(p.Asn172del)mutation site changed,which was suspected to be pathogenic mutations.Combined with the patients clinical manifestations,family characteristics and genetic test results,the patients were finally diagnosed with pachyonychia congenita type 6b.Conclusion Heterozygous variation of KRT6Bgene c.516＿518delCAA(p.Asn172del)may be the cause of pachyonychia congenita type 6bin this family.更多还原