Analysis Of Gene Mutation And Skin Imaging Of Isolated Caf(?)-Au-Lait Macules

Background:Caf（?）-au-lait macules（CALMs）are a common pigmented hyperplastic skin disease,CALMs are light brown or coffee patches of different shapes with smooth surfaces and uniform color.Multiple CALMs that have six or more can be associated with neurofibromatosis type 1（NF1）and other genetic syndromes.Isolated CALMs are defined as multiple café-au-lait macules in patients without any other sign of NF1.Typical CALMs have predictive significance for NF1 and non-invasive techniques can provide more accurate results for judging whether café-au-lait spots are typical.It is necessary to provide the diagnostic basis for isolated CALMs through skin imaging technology and improve the level of diagnosis and treatment.This article is the first time to combine Dermoscopy and Reflection Confocal Microscopy（RCM）which are two non-invasive auxiliary examinations to record the skin image characteristics of CALMs.In recent years,great progress has been made in the study of the molecular pathogenesis of NF1,and this article will be systematically summarized.Objectives:1.This study aimed to study the NF1 gene mutations in the families of six Han isolated CALMs patients,using ANNOVAR software to screen out pathogenic mutations and expand the NF1 gene mutation spectrum.Literature review was conducted to analyze the genotypic phenotypic characteristics of NF1 to provide assistance for clinical diagnosis and treatment.2.Dermoscopy and Reflectance Confocal Microscopy examination were performed on six isolated CALMs patients to summarize the characteristics of isolated CALMs skin imaging to provide a basis for clinical diagnosis and differential diagnosis.Methods:1.In this study,we included six isolated CALMs families as study subjects,used questionnaires to collect basic clinical information from patients,and we used generation sequencing to detect NF1 gene mutation in these six families,next-generation sequencing（NGS）was performed on two families,and the next-generation sequencing results of the two families were analyzed by bioinformatics to summarize the gene mutations that may cause disease.2.The published literature in Pub Med and other databases was reviewed,isolated CALMs and NF1 gene mutations were summarized,genotype-phenotypic analysis was performed.3.Skin imaging analysis was performed in combination with dermoscopy and RCM in these six isolated CALMs patients.Results:1.We were able to identify gene mutations in this study by using Sanger sequencing on20 individuals from six families and WES on 7 individuals from the first and third families.2.The first two families each identified one novel mutation in NF1.In the first family,a missense mutation [c.7355G>A（p.Arg2452His;NM₀01042492.2）]was detected in the proband,the proband’s sister,and the proband’s mother,considered a causative mutation after the software analysis and not previously reported.In the second family,a frameshift mutation[c.2739₂740del AC（p.I913Mfs*5;NM₀01042492.2）] was detected in the proband,considered a causative mutation in NF1 after software analysis and not previously reported.The proband of the first,fourth,fifth,and sixth families identified a heterozygous mutation [c.2034G>A（p.P678P;NM₀01042492.2）],software analysis is considered as polymorphism sites（SNP）.The proband in the second proband identified a heterozygous mutation [c.702G>A（p.L234L;NM₀01042492.2）],software analysis is considered as polymorphism sites（SNP）.3.According to NF1 genotype-phenotypic analysis,a higher number of CALMs were observed in patients with frameshift mutations compared to patients with missense mutations,the probability of appearing atypical CALMs is greater,and our study complied with the rule.4.Dermoscopy showed uniform and consistent tan-pigmented network patches or dendritic patches with defined margins,round or circular,variable in size and can exhibit a grid-like pattern.The pigmentation around the hair follicles is reduced and no vasodilation was seen.Under RCM,CALMs were manifested as an increase in the total amount of melanin in the epidermis,an increase in pigment particles in the basal layer,and a notable increase in high-refractive substances.The melanocytes were arranged regularly,with no dendritic structures and heteromorphic cells observed,no obvious abnormalities in the superficial dermis.Conclusion:1.In this study,two novel pathogenic mutation sites[c.7355G>A（p.Arg2452His;NM₀01042492.2）]and[c.2739₂740del AC（p.I913Mfs*5;NM₀01042492.2）]were identified in NF1,which expanded the NF1 gene mutation spectrum and provided evidence for early diagnosis of the disease.2.In this study,the imaging features of CALMs were described for the first time by combining dermoscopy and RCM which provided a reference for early non-invasive diagnosis and differential diagnosis of this disease.