Mutational Analysis Of The NEMO Genes In One Incontinentia Pigmenti Family

Background Incontinentia pigmenti（IP）,is a rare X-linked dominant genetic disease characterized by skin lesions and can also involve teeth,hair,eyes,bones,central nervous system and other organ systems.The characteristic skin lesions can be divided into four stages: stage 1: erythema blister stage;stage 2: verrucous hyperplasia stage;stage 3: pigmentation stage;stage 4: atrophy stage.The pathogenic gene of the disease is NEMO gene,the main mutation type is exon 4-10 mutation,accounting for about80%-90%,and the rest are point mutation,repetition,microdeletion and so on.However,no clear genotype-phenotypic correlation has been found.ObjectiveUsing clinical manifestations,reflexion confocal microscope and genetic testing to diagnosis IP and to identify pathogenic mutation.Analyzing the NEMO mutation and clinical features of Chinese IP cases by a literature search.MethodsCollecting the data of all patients,using reflexion confocal microscope to clear the lesion structure.The peripheral blood of patients and normal people in this family were collected.In order to exclude the genetic diversity,we also collected 100 healthy controls.NEMO gene sequence was obtained from Universityof California Santa Cruz（UCSC）and primers were designed.Sanger sequencing was performed after amplification.The frequency of variation was originated from 1000 genomes,NCBI and Ex AC.American College of Medical Genetic and Genomics（ACMG）guidelines were used to evaluate the pathogenic potential of DNA sequence alteration.A literature search was performed using Pub Med,CNKI,VIP.Data of clinical features and NEMO mutation of Chinese incontinentia pigmenti cases were analyzed.Results1.All the 4 patients in this family had typical skin lesions,and there were some differences in other symptoms.2.The RCM of the proband’mother showed that: compared with the normal skin,the pigment content in the basal layer of the epidermis in the hypopigmentation area decreased,the structure of the pigment ring was complete,and the pigment content in the basal layer of the pigmentation area increased.3.Genetic testing indicated that there was a heterozygous nonsense mutation c.1153C>T（p.Gln385X）in exon 8 of NEMO gene in 4 patients which was not found in 14 healthy relatives and 100 healthy controls,which resulting in the mutation of glutamine to stop codon at position 385 of encoded protein.4.Database showed that the mutation was a novel nonsense mutation.ACMG guidelines determined that the mutation was PVS1.These evidence confirmed the final diagnosis of Incontinentia Pigmenti.Conculsions1.NEMO gene mutation（c.1153C>T）is associated with IP in this family.Although the affected family members had identical mutations,diferences in the clinical manifestations of these family members were observed,which reveals the complexity of the phenotype-infuencing factors in IP.2.The characteristics of clinical phenotype and gene mutation of pigmented incontinence in China were summarized.Among Chinese IP patients,86.1% were female,74.6% were sporadic,only 25.4% had a family history of IP,and 94.3%IP patients developed the disease within 1 month after birth.All patients with IP had typical IP lesions,and stage 1 and stage 3 lesions were the most common.Among the extradermal manifestations,nervous system and eye involvement are the most common.The positive rate of histopathological examination was high.Among the patients who underwent genetic testing,the detection rate of NEMO gene mutation was about 72.1%.NEMO4-10 exon deletion was the most common mutation type.