A novel mutation of keratin 5 in epidermolysis bullosa simplex with migratory circinate erythema

Epidermolysis bullosa simplex migratory circinate erythema (EBS-Migr) is an uncommon subtype of EBS. We report a case of EBS-MIGR with a novel heterozygous pathogenic mutation in exon 9 (frameshift deletion c.1650delC) and likely benign heterozygous mutation in exon 2 (missense c.591C > A) of keratin 5. This novel pathogenic mutation in KRT5 expands the molecular spectrum of this rare subtype of EBS.     

Identification of novel and known KRT5 and KRT14 mutations in 53 patients with epidermolysis bullosa simplex: correlation between genotype and phenotype

Background Basal epidermolysis bullosa simplex (EBS) is a hereditary skin blistering disorder resulting in most cases from missense mutations in the keratin 5 (KRT5) or keratin 14 (KRT14) genes. Objectives To identify the underlying mutations in different EBS subtypes and correlate genotype and phenotype. Methods Mutation analysis was performed in 53 patients with EBS and their families by direct sequencing of the KRT5 and KRT14 genes. Results We identified 39 different mutations, of which 15 have not been published previously. Three novel deletion/insertion mutations, among them one in‐frame duplication, were associated with the rare phenotype of EBS with mottled pigmentation. We identified for the first time a patient with compound heterozygosity for KRT5 mutations causing Dowling–Degos disease and EBS. Conclusions Identification of novel mutations and genotype–phenotype correlations in EBS allow improved understanding of disease pathogenesis as well as better patient management.     

The clinical spectrum of epidermolysis bullosa simplex

As part of the U.K. National Epidermolysis Bullosa Register, we have systematically recorded clinical information on 130 (77%) of the 168 known Scottish epidermolysis bullosa simplex (EBS) sufferers. Three subtypes of EBS were recognized: Dowling–Meara (EBS‐DM), Weber–Cockayne (EBS‐WC) and Köbner (EBS‐Kb), seen in 5%, 42% and 53% of patients, respectively. As there is considerable overlap between EBS‐WC and EBS‐Kb, with both phenotypes frequently seen within the same pedigree, EBS‐WC is best regarded as a milder variant of EBS‐Kb rather than a separate disorder. Improvement with age is common in all variants of EBS, but is not invariable. Pain due to acral blistering in EBS‐Kb/EBS‐WC has a more marked impact on life‐style than the blisters of EBS‐DM. Oral blistering, nail involvement and aplasia cutis congenita occur in all EBS subtypes and laryngeal involvement is a feature of EBS‐DM. Seasonal variation is not seen in EBS‐DM but is common in EBS‐Kb/EBS‐WC.     

Clinical and molecular features in a cohort of Middle Eastern patients with epidermolysis bullosa

Background

Epidermolysis bullosa (EB) features skin and mucosal fragility due to pathogenic variants in genes encoding components of the cutaneous basement membrane. Based on the level of separation within the dermal-epidermal junction, EB is sub-classified into four major types including EB simplex (EBS), junctional EB (JEB), dystrophic EB (DEB), and Kindler EB (KEB) with 16 EB-associated genes reported to date.

Methods

We ascertained a cohort of 151 EB patients of various Middle Eastern ethnic backgrounds.

Results

The cohort was comprised of EBS (64%, 97/151), DEB (21%, 31/151), JEB (12%, 18/151), and KEB (3%, 5/151). KRT14 and KRT5 variants were most common among EBS patients with 43% (42/97) and 46% (45/97) of EBS patients carrying mutations in either of these two genes, respectively. Truncal involvement was more common in KRT14-associated EBS as compared to EBS due to KRT5 mutations (p < .05). Mutations in COL17A1 and laminin 332-encoding genes were identified in 55% (10/18) and 45% (8/18) of JEB patients. Scarring alopecia, caries, and EB nevi were most common among JEB patients carrying COL17A1 mutations as compared to laminin 332-associated JEB (p < .05). Abnormal nails were evident in most DEB and JEB patients while poikiloderma was exclusively observed in KEB (p < .001).

Conclusions

EB patients of Middle Eastern origin were found to feature specific phenotype–genotype correlations of relevance to the diagnosis and genetic counseling of patients in this region.     

Severe epidermolysis bullosa simplex phenotype caused by codominant mutations p.Ile377Thr in keratin 14 and p.Gly138Glu in keratin 5

Epidermolysis bullosa simplex (EBS) is a rare skin disease usually inherited in an autosomal dominant pattern. EBS is resulting from mutations in keratin 5 (KRT5) and keratin 14 (KRT14) genes encoding the keratins 5 and 14 proteins expressed in the keratinocytes of the basal layer of the epidermis. To date, seven pathogenic mutations have been reported to be responsible for EBS in the Canadian population from the province of Quebec: p.Pro25Leu, p.Leu150Pro, p.Met327Thr and p.Arg559X in KRT5; p.Arg125Ser, p.Ile377Thr and p.Ile412Phe in KRT14. Here, we present a novel French-Canadian patient diagnosed with EBS confined to the soles but presenting a severe complication form including blisters, hyperkeratosis, skin erosions and toenail abnormalities. Mutation screening was performed by direct sequencing of the entire coding regions of KRT5 and KRT14 genes and revealed the previously reported missense heterozygous mutation c. 1130T > C in KRT14 (p.Ile377Thr). Furthermore, this patient is carrying a second mutation in KRT5, c.413G > A (p.Gly138Glu), which has been linked to an increased risk of basal cell carcinoma in the literature. We suspect an impact of the p.Gly138Glu variant on the EBS phenotype severity of the studied patient. The pathogenicity and consequences of both genetic variations were simulated by in silico tools.     

Keratin mutations in patients with epidermolysis bullosa simplex: correlations between phenotype severity and disturbance of intermediate filament molecular structure

Background Epidermolysis bullosa simplex (EBS) is an inherited skin disorder caused by mutations in the keratin 5 (KRT5) and keratin 14 (KRT14) genes, with fragility of basal keratinocytes leading to epidermal cytolysis and blistering. Objectives In this study, we characterized mutations in KRT5 and KRT14 genes in patients with EBS and investigated their possible structure–function correlations. Materials and methods Mutations were characterized using polymerase chain reaction (PCR) and DNA sequencing. Further, to explore possible correlations with function, the structural effects of the mutations in segment 2B of KRT5 and KRT14 and associated with EBS in our patients, as well as those reported previously, were modelled by molecular dynamics with the aid of the known crystal structure of the analogous segment of human vimentin. Results We have identified mutations in the KRT5 and KRT14 genes in 16 of 23 families affected by EBS in the Czech Republic. Eleven different sequence variants were found, of which four have not been reported previously. Novel mutations were found in two patients with the EBS‐Dowling–Meara variant (EBS‐DM) [KRT14‐p.Ser128Pro and KRT14‐p.Gln374_Leu387dup(14)] and in three patients with localized EBS (KRT14‐p.Leu136Pro and KRT5‐p.Val143Ala). Molecular dynamics studies show that the mutations p.Glu411del and p.Ile467Thr perturb the secondary alpha‐helical structure of the mutated polypeptide chain, the deletion p.Glu411del in KRT14 has a strong but only local influence on the secondary structure of KRT14, and the structural impact of the mutation p.Ile467Thr in KRT5 is spread along the helix to the C‐terminus. In all the other point mutations studied, the direct structural impact was significantly weaker and did not destroy the alpha‐helical pattern of the secondary protein structure. The changes of 3‐D structure of the KRT5/KRT14 dimer induced by the steric structural impact of the single point mutations, and the resulting altered inter‐ and intramolecular contacts, are spread along the protein helices to the protein C‐terminus, but the overall alpha‐helical character of the secondary structure is not destroyed and the atomic displacements induced by mutations cause only limited‐scale changes of the quaternary structure of the dimer. Conclusions The results of molecular modelling show relationships between patients’ phenotypes and the structural effects of individual mutations.     

Novel KRT14 mutation causing epidermolysis bullosa simplex with variable phenotype

About 75% of cases of epidermolysis bullosa simplex result from mutations in KRT5 and KRT14 genes. Here, we report a family with a novel heterozygous missense mutation p.Leu418Gln in the KRT14 gene causing EBS of phenotype varying from EBS‐loc to EBS‐gen intermed. To the best of our knowledge, the family reported by us is the largest one in which two different phenotypes can be distinguished. The molecular dynamics simulations show that p.Leu418Gln mutation results in clear disruption of intermolecular π‐stacking between KRT14:Tyr415 and KRT5:Tyr470, which in turn may affect putative phosphorylation site at KRT14:Thr414. This study further supports the importance of the EIATYR/KLLEGE motif in maintaining structural stability of KRT14:KRT5 heterodimer and indicates that physical properties of introduced amino acid can modulate the disease severity. The results obtained indicate further need of genotype–phenotype studies in EBS. In conclusion, genotype‐based prognosis should be given to patients with caution.     

The Birmingham Epidermolysis Bullosa Severity score: development and validation

Background Objective severity scores facilitate clinical care and research. However, the rarity and heterogeneity of epidermolysis bullosa (EB) make scoring difficult. Objectives To develop a severity score covering all subtypes of EB at all ages that is simple, valid, sensitive and reliable. Methods Score items and weightings were generated by expert consensus, and refined for content and face validity. The Birmingham EB Severity (BEBS) score was tested on 97 patients aged 0–64 years. Results Eleven items were scored: area of damaged skin, involvement of nails, mouth, eyes, larynx and oesophagus, scarring of hands, skin cancer, chronic wounds, alopecia and nutritional compromise. Area was allocated 50 points, and the 10 other items 5 points each, giving a maximum score of 100. Lowest BEBS scores occurred in Weber–Cockayne EB simplex (median 1·0; range 0·1–3·0; n = 12), highest scores in generalized non‐Herlitz junctional EB (28·5; 5·0–62·0; n = 7), Hallopeau–Siemens recessive dystrophic EB (HS‐RDEB) (22·9; 4·3–69·0; n = 23) and Herlitz junctional EB (H‐JEB) (14·4; 2·5–49·3; n = 9), and intermediate scores in dominant dystrophic EB (5·3; 0·5–15·9; n = 19), Dowling–Meara EB simplex (DM‐EBS) (6·3; 2·8–22·5; n = 16) and non‐Hallopeau–Siemens recessive dystrophic EB (7·8, 2·8–27·8; n = 11). Intra‐ and interobserver correlations were high. With age, scores increased for H‐JEB (r = 0·9, P = 0·001) and HS‐RDEB (r = 0·73, P = 0·001) and decreased for DM‐EBS (r = ?0·62, P = 0·01), with positive but nonsignificant correlations for the other types. Conclusions The BEBS score appears valid and reproducible, gives appropriate scores for different subtypes, and reflects changes with age.     

Weber-Cockayne亚型单纯型大疱性表皮松解症一家系KRT5基因突变

【摘要】　目的　研究Weber-Cockayne亚型单纯型大疱性表皮松解症(EBS)一家系的K5基因突变情况,为该病的基因诊断与遗传咨询提供依据。方法　收集一个Weber-Cockayne亚型单纯型大疱性表皮松解症的家系临床资料,采用聚合酶链反应及DNA直接测序的方法对家系内成员进行K5基因突变检测,同时对50名无亲缘关系正常对照者的该位点进行直接测序。针对所发现的突变,以限制性内切酶片段长度多态性分析加以验证。结果　该家系中所有患者均存在K5基因错义突变I 161S,而在家系内正常人及50名无亲缘关系的正常对照者中均未发现该突变。结论　K5基因错义突变I161S是导致此家系中患者临床表现的特异突变。     

A novel nonsense mutation at E106 of the 2B rod domain of keratin 14 causes dominant epidermolysis bullosa simplex

Epidermolysis bullosa simplex (EBS) is classified into three main types and is caused, in most case s , by missense mutations in the genes encoding keratin (K) 5 and K14. In this study, we clinically, ultrastructurally, immunohistochemically, and molecularly studied a patient with a dominant EBS, Köbner type. Using sequence analysis of genomic DNA, a novel K14 nonsense mutation was identified. A heterozygous mutation G1231T of KRT14 was found to be associated with the disease in the patient. The mutation created a premature stop codon (amino acid codon 411, residue 106 of the 2B helix) in the K14 molecule. This residue lies in a highly conserved region and was recently found to be absolutely required for molecular stability and intermediate filament assembly in K5 and K14. The E411X (E106X) heterozygous ablation, missing the last 16 amino acid residues of the 2B and the entire tail domain of K14, led to disease but did not result in clumping of keratin filaments. It is the first premature stop codon mutation of K14 found in dominant EBS.     

Novel keratin 14 gene mutations in patients from Hungary with epidermolysis bullosa simplex

Mutations in genes keratin 5 (KRT5) and 14 (KRT14) encoding the basal type keratin intermediate filaments have been identified in epidermolysis bullosa simplex (EBS) families and are likely to cause skin fragility. Three novel keratin 14 mutations in cases from the Hungarian Epidermolysis Bullosa Centre are reported. In a 7-year-old boy with Dowling-Meara type EBS (DM-EBS), who had severe skin symptoms with extended herpetiform blisters, a novel amino acid substitution N123K in keratin 14 had been detected. A 26-year-old woman with mild DM-EBS with prominent palmoplantar hyperkeratosis and without active blister formation had a novel R125G mutation in keratin 14. In a 6-year-old girl, with Weber-Cockayne type EBS (WC-EBS) with palmoplantar blisters and moderate mental retardation, a novel V133L substitution was detected. Her pedigree showed autosomal dominant mode of inheritance; in the two other families, only the index patients were affected. The N123K and R125G mutations causing DM-EBS phenotypes are located within the helix initiation motif of the rod domain, whereas the very close V133L mutation underlying the WC-EBS phenotype is outside of this region. These novel amino acid substitutions provide further information for genotype-phenotype correlation in KRT14 mutations, and demonstrate the first molecular genetic data in EBS patients from Hungary.     

Epidermolysis bullosa simplex in Japanese and Korean patients: genetic studies in 19 cases

BACKGROUND: Epidermolysis bullosa simplex (EBS) comprises a group of hereditary bullous diseases characterized by intraepidermal blistering caused by mutations in either keratin gene, KRT5 or KRT14. Significant correlation between the position of mutations within these proteins and the clinical severity of EBS has been noted. A recent report showed EBS cases in Israel had unique genetic features compared with European or U.S.A. associated families, which suggests that the ethnic and geographical features of EBS patients may be different. OBJECTIVES: To assess the possibility that EBS may present with certain specific features in Japanese and Koreans and to identify additional EBS mutations for genotype/phenotype correlation. METHODS: EBS was clinically diagnosed and confirmed by transmission electron microscopic examination of a skin biopsy. Mutation analysis of KRT5 and KRT14 was performed by direct sequencing in 17 Japanese and two Korean EBS patients. RESULTS: We have identified six novel KRT5 missense mutations (V143D, D158V, V186M, Q191P, R352S, G517D). R352S is the first mutation in the 2A domain. Most of these novel mutations changed amino acids that were evolutionarily conserved. Eight including all five mutations in EBS-Dowling-Meara patients have been previously reported. We were unable to detect mutations in five sporadic EBS-Koebner patients. The proportion of mutations in KRT5 (11 of 14; 78%) is higher than that for KRT14 mutations (3 of 14; 21%) in these Japanese and Korean EBS patients. CONCLUSIONS: Japanese and Korean patients with EBS showed very similar phenotype and genotype correlations with patients from Western countries. Whether the higher proportion of KRT5 mutations is a definite characteristic of Japanese and Korean patients with EBS or not, requires further research into mutations in Japanese and Korean people.     

Novel mutation (Asp158Val) in H1 domain of keratin 5 gene in a Japanese patient with Köbner-type epidermolysis bullosa simplex

We describe a 19‐year‐old Japanese male with Köbner‐type epidermolysis bullosa simplex (EBS‐KB) with a novel keratin gene mutation. The patient developed blisters on the feet, palms, elbows and knees soon after birth. His father is similarly affected with blistering, but his mother and younger brother are not affected. Histological examination revealed that the primary separation in the blister occurred within the basal cell layer. Sequence analysis demonstrated an A‐to‐T transition at the second position of codon 158 in the keratin 5 (K5) gene. The amino acid at codon 158 was deduced to have changed from asparagine to valine. We identified a novel mutation (Asp158Val) in the H1 domain of the K5 gene in this Japanese patient with EBS‐KB. This is the first gene mutation report of EBS‐KB in the H1 domain of the K5 gene.     

Functional testing of keratin 14 mutant proteins associated with the three major subtypes of epidermolysis bullosa simplex

Epidermolysis bullosa simplex (EBS) is a group of autosomal dominantly inherited skin disorders characterized by the development of intra-epidermal skin blisters on mild mechanical trauma. The three major clinical subtypes (Weber-Cockayne, Koebner and Dowling-Meara) are all caused by mutations in either the keratin 5 (KRT5) or keratin 14 (KRT14) gene. Previously, we identified three novel KRT14 missense mutations in Danish EBS patients associated with the three different forms of EBS (1). The identified KRT14 mutations represent the full spectrum of the classical EBS subtypes. In the present study we investigated these mutations in a cellular expression system in order to analyse their effects on the keratin cytoskeleton. KRT14 expression vectors were constructed by fusing the nucleotide sequence encoding the FLAG reporter peptide to the 3' end of the KRT14 cDNA sequences. The expression vectors were transiently transfected into normal human primary keratinocytes (NHK), HaCaT or HeLa cells in order to analyze the ability of the mutant K14 proteins to integrate into the existing endogenous keratin filament network (KFN). No effect on the keratin cytoskeleton was observed upon transfection of NHK with the various K14 constructs neither with nor without a subsequently induced heat-stress. In contrast, all constructs, including wild-type K14, caused collapse of the endogenous KFN in a small fraction of the transfected HeLa and HaCaT cells. However, overexpression of the mutation associated with the most severe form of the disease, EBS Dowling-Meara, resulted in a higher number of transfected HaCaT cells with KFN collapse (P < 0.001). Thus, although a background KFN perturbance was observed upon transfection with the wild-type K14 construct, the mutant protein associated with the most severe form of EBS worsened the KFN perturbation significantly compared with the mutant proteins associated with the milder forms of the disease and the normal K14 protein. This shows that the clinical severity of disease-associated mutations identified in patients can be tested using this expression system, although it can not at present be used to discriminate between the milder forms. Assessment of the endogenous K14 protein expression in NHK and HaCaT cells indicated that the higher level of endogenous keratin expression in NHK might make these cells more resistant to perturbation of the keratin cytoskeleton by overexpressed K14 protein than HaCaT cells.     

Plectin abnormality in epidermolysis bullosa simplex Ogna: non-responsiveness of basal keratinocytes to some anti-rat plectin antibodies

Abstract Epidermolysis bullosa (EB) is a heterogeneous group of genetic bullous skin diseases. The EB simplex group (EBS) is characterized by intraepidermal blistering. EBS-Ogna was first described as a separate entity based on clinical studies. Later genetic linkage of EBS-Ogna to the GPT locus for glutamate pyruvate transaminase (alanine transaminase) was delected and GPT was assigned to chromosome 8. then to the terminal long arm band 8q24. Plectin is an abundant and widespread cytoskeletal protein which has been proposed as a general crosslinking element of intermediate filaments. Human plectin has recently been cloned and in situ hybridized to chromosome 8q24. To examine whether plectin could be associated with EBS-Ogna we performed an immunohistochemical study with a panel of mAbs to rat plectin. Interestingly, 2 of these mAbs showed strong intracellular staining of the suprabasal and basal layer of the epidermis in all control samples, whereas no reactivity of the basal layer was found in the Ogna group. These results strongly suggest that plectin is involved in the pathogenesis of EBS-Ogna.     

Generation and characterization of epidermolysis bullosa simplex cell lines: scratch assays show faster migration with disruptive keratin mutations

BACKGROUND: Epidermolysis bullosa simplex (EBS) is an inherited skin fragility disorder caused by mutations in keratin intermediate filament proteins. While discoveries of these mutations have increased understanding of the role of keratins and other intermediate filaments in epithelial tissues, progress towards the development of therapy for these disorders is much slower. OBJECTIVES: Cell culture model systems that display these structural defects are needed for analysis of the cellular consequences of the mutations and to enable possible therapeutic strategies to be developed. Our aim was to generate immortalized cell lines as such model systems for the study of EBS. METHODS: We generated a series of stable cell lines expressing EBS-associated keratin mutations, by immortalizing keratinocytes from EBS-affected skin biopsies with either simian virus 40 (SV40) T antigen or human papillomavirus 16 (HPV16) E6/E7, and assessed their keratin expression (by immunofluorescence), proliferation rates and migratory behaviour (in outgrowth and scratch wound assays). RESULTS: Clonal immortalized keratinocyte cell lines KEB-1, KEB-2, KEB-3 (using SV40 T antigen) and KEB-4, KEB-7 and NEB-1 (using HPV16 E6/E7) were established. These include two lines from a single individual with Weber-Cockayne EBS (i.e. KEB-3 and KEB-4, mutation K14 V270M), and three cell lines from a second family, two from siblings carrying the same mutation (KEB-1, KEB-2 lines from Dowling-Meara EBS, mutation K5 E475G) and one from an unaffected relative (NEB-1). The sixth cell line (KEB-7), with a previously unreported severe mutation (K14 R125P), was the only one to show keratin aggregates in resting conditions. Despite variations in the immortalization procedure, there was no significant difference between cell lines in keratin expression, outgrowth capabilities or response to transient heat shock. However, cell migration, as measured by speed of scratch wound closure, was significantly faster in cells with severe EBS mutations. CONCLUSIONS: These cell lines provide useful culture systems in which to assess aspects of EBS-induced cell changes. The faster migration after scratch wounding of the EBS keratinocytes may be a consequence of the known upregulation of stress-activated kinase pathways in these cells.     

Impact of inherited epidermolysis bullosa on parental interpersonal relationships, marital status and family size

BACKGROUND: The presence in a family of a child or children with epidermolysis bullosa (EB) may have profound psychological implications for other family members. OBJECTIVES: To assess the impact of the presence of EB in one or more children on the personal relationships between their parents. METHODS: Standardized questionnaires were used. RESULTS: In general, the presence of a child severely affected with EB had profound effects on many aspects of marriage. This included a lack of interest in participating in activities as couples [junctional EB (JEB), 45%; recessive dystrophic EB (RDEB), 25%], a lack of energy to invest in such pursuits (JEB, 82%; RDEB, 50%), limitations in opportunities for sharing nonintimate physical activities (reported by most parents having children with some type of generalized EB), and negatively altered parental sex life (JEB, 55%; RDEB, 39%). This is consistent with the fact that 10%, 64%, 25% and 36% of parents of an affected child with EB simplex (EBS), JEB, dominant dystrophic EB (DDEB) and RDEB, respectively, characterized their relationships as couples as revolving almost exclusively around the day-to-day care of their affected children. The severity of disease in an affected child clearly influenced parental decisions about having more children: 24% and 64% of parents of children with JEB and RDEB, respectively, chose not to have additional children, compared with 26% and 54% of parents with children having EBS or DDEB. This choice was most often pursued via tubal ligation; less often, alternative means of surgical sterilization were chosen. Divorce was common among parents of children with EB (range: 17% in EBS to 31% in JEB) and, with the exception of parents of children with EBS, was usually directly attributed by one or both parents to the profound impact that this disease had exerted on their marriage. CONCLUSIONS: Physicians caring for children with EB need to give more consideration to the many psychological factors that may contribute to their patients' well being. They may need to assist these children's parents in seeking support and counselling to prevent destruction of the family unit.     

A keratin 14 'knockout' mutation in recessive epidermolysis bullosa simplex resulting in less severe disease

Epidermolysis bullosa simplex (EBS) is a blistering skin disease caused in most cases by mis-sense mutations in genes encoding the basal epidermal keratin (K) 5 and K14. The inheritance is usually autosomal dominant and the mutant keratin proteins appear to exert a dominant negative effect on the keratin intermediate filament cytoskeleton in basal keratinocytes. We report a child with a homozygous K14 mutation resulting in the complete absence of K14 protein in the epidermis; remarkably, he only had mild to moderate disease. Electron microscopy of a skin biopsy showed a marked reduction in numbers of keratin intermediate filaments in the basal keratinocytes. Immunofluorescence microscopy using monoclonal antibody LL001 against K14 showed no staining, suggesting a functional knockout of K14. Sequence analysis of genomic DNA revealed a homozygous mutation in codon 31 of K14 that resulted in a premature stop codon further downstream in exon 1. The child's mother, who is unaffected by the disease, is heterozygous for the mutation. The consanguineous father was unaffected and unavailable for testing. The resulting mRNA is predicted to encode a protein of 116 amino acids, of which the first 30 are identical to the normal K14 sequence, and the remaining 86 residues are mis-sense sequence. Four previously reported cases of autosomal recessive EBS with functional knockout of K14 were severely affected by blistering, in contrast to our patient in whom the predicted protein has only the first 30 amino acids of K14 and is therefore the closest to a true knockout of K14 protein yet identified.     

Identification of two rare and novel large deletions in ITGB4 gene causing epidermolysis bullosa with pyloric atresia

Epidermolysis bullosa with pyloric atresia (EB‐PA) is a rare autosomal recessive hereditary disease with a variable prognosis from lethal to very mild. EB‐PA is classified into Simplex form (EBS‐PA: OMIM #612138) and Junctional form (JEB‐PA: OMIM #226730), and it is caused by mutations in ITGA6, ITGB4 and PLEC genes. We report the analysis of six patients with EB‐PA, including two dizygotic twins. Skin immunofluorescence epitope mapping was performed followed by PCR and direct sequencing of the ITGB4 gene. Two of the patients presented with non‐lethal EB‐PA associated with missense ITGB4 gene mutations. For the other four, early postnatal demise was associated with complete lack of β4 integrin due to a variety of ITGB4 novel mutations (2 large deletions, 1 splice‐site mutation and 3 missense mutations). One of the deletions spanned 278 bp, being one of the largest reported to date for this gene. Remarkably, we also found for the first time a founder effect for one novel mutation in the ITGB4 gene. We have identified 6 novel mutations in the ITGB4 gene to be added to the mutation database. Our results reveal genotype–phenotype correlations that contribute to the molecular understanding of this heterogeneous disease, a pivotal issue for prognosis and for the development of novel evidence‐based therapeutic options for EB management.     

伴移行性环形红斑的单纯性大疱性表皮松解症一家系报道及基因检测

目的:单纯性大疱性表皮松解症伴有移行性环状红斑(EBS-Migr)是EBS的一种罕见亚型,是一种常染色体显性遗传病,本文报道一家系,并进行基因检测。方法:收集临床资料,提取患儿及其父母外周血DNA,对患儿及其父母进行全基因组外显子测序,经生物学分析,获得致病变异;再采用Sanger测序法进行验证。结果:患儿及其父亲KRT5外显子9存在杂合突变(移码缺失c.1653_1654delCT),其母亲未发现该突变。结论:该患儿诊断为伴移行性环状红斑的单纯性大疱性表皮松解症,致病机制为KRT5外显子9发生杂合突变(移码缺失c.1653_1654delCT),既往未见报道。