Form Of Epidermolysis Bullosa Simplex Research Articles

Epidermolysis Bullosa: Two rare case reports of COL7A1 and EBS-GEN SEV KRT14 variants with review of literature

EpidermolysisBullosa is a rare hereditary skin condition that causes blisters. Genes encoding structural proteins at or near the dermal-epidermal junction are mutated recessively or dominantly, and this is the primary cause of EB. Herein, two Chinese boys were diagnosed with the condition, each with a different variant in a gene that serves as a reference for EB genetic counseling. Skincare significantly impacted their prognosis and quality of life.Case presentationTwo Chinese boys, with phenotypically normal parents, have been diagnosed with distinct blister symptoms, one with Dominant Dystrophic Epidermolysis Bullosa and the other with a severe form of Epidermolysis Bullosa Simplex. The first patient had a G-to-A variant in the COL7A1 allele, at nucleotide position 6163 which was named “G2055A”. The proband is heterozygous for Dystrophic Epidermolysis Bullosa due to a COL7A1 allele with a glycine substitution at the triple helix domain. A similar variant has been discovered in his mother, indicating its potential transmission to future generations. Another patient had severe Epidermolysis Bullosa Simplex with a rare c.377T > A variant resulting in substitution of amino acid p.Leu126Arg (NM_000526.5 (c.377T > G, p.Leu126Arg) in the Keratin 14 gene. In prior literature, Keratin 14 has been associated with an excellent prognosis. However, our patient with this infrequent variant tragically died from sepsis at 21 days old. There has been a reported occurrence of the variant only once.ConclusionOur study reveals that Epidermolysis Bullosa patients with COL7A1 c.6163G > A and KRT14 c.377T>A variants have different clinical presentations, with dominant forms of Dystrophic EB having milder phenotypes than recessive ones. Thus, the better prognosis in the c.6163G > A patient. Furthermore, c.377T>A patient was more prone to infection than the patient with c.6163G>A gene variant. Genetic testing is crucial for identifying the specific variant responsible and improving treatment options.

A novel KRT14 null mutation leads to autosomal recessive epidermolysis bullosa simplex.

We describe a novel homozygous KRT14 (also known as K14) mutation detected in a patient with a relatively mild form of epidermolysis bullosa simplex (EBS). Our patient harbours loss of function of both alleles of the KRT14 gene. This is the 16th reported mutation of recessive EBS in KRT14.

301 The Spectrum of PLEC Sequence Variants and Related Plectinopathies Including Novel Association with Epidermolysis Bullosa Pruriginosa

Plectin, a cytoskeletal linker and intermediate filament protein ubiquitously expressed in many cell types, is encoded by PLEC. Plectin consists of three main domains that determine its functionality: the N-terminal domain, the rod domain, and the C-terminal domain. Molecular defects in PLEC correlating with the functional aspects lead to a group of rare heritable disorders, plectinopathies. These multisystem disorders include an autosomal dominant form of epidermolysis bullosa simplex (EBS-Ogna), limb girdle muscular dystrophy (LGMD), and an autosomal recessive form of epidermolysis bullosa simplex (EBS), which may associate with muscular dystrophy (EBS–MD), pyloric atresia (EBS–PA), and/or congenital myasthenic syndrome (EBS-MyS).

Mutation update: The spectra of PLEC sequence variants and related plectinopathies.

Plectin, encoded by PLEC, is a cytoskeletal linker of intermediate filaments expressed in many cell types. Plectin consists of three main domains that determine its functionality: the N-terminal domain, the Rod domain, and the C-terminal domain. Molecular defects of PLEC correlating with the functional aspects lead to a group of rare heritable disorders, plectinopathies. These multisystem disorders include an autosomal dominant form of epidermolysis bullosa simplex (EBS-Ogna), limb-girdle muscular dystrophy (LGMD), aplasia cutis congenita (ACC), and an autosomal recessive form of EBS, which may associate with muscular dystrophy (EBS-MD), pyloric atresia (EBS-PA), and/or congenital myasthenic syndrome (EBS-MyS). In this study, genotyping of over 600 Iranian patients with epidermolysis bullosa by next-generation sequencing identified 15 patients with disease-causing PLEC variants. This mutation update analyzes the clinical spectrum of PLEC in our cohort and in the literature and demonstrates the relationship between PLEC genotype and phenotypic manifestations. This study has integrated our seven novel PLEC variants and phenotypic findings with previously published data totaling 116 variants to provide the most complete overview of pathogenic PLEC variants and related disorders.

Generalised Epidermolysis Bullosa with Severe Anaemia in an Adolescent: A Case Report

EBS is a rare genodermatosis usually inherited in an autosomal dominant fashion, although rare autosomal recessive cases have been reported. In severe generalised EBS, infants exhibit severe symptoms at the onset which tend to improve with time. We report an adolescent with severe generalised epidermolysis bullosa simplex (EBS), the most severe form of EBS, with severe iron deficiency anaemia

A cell-based drug discovery assay identifies inhibition of cell stress responses as a new approach to treatment of epidermolysis bullosa simplex.

ABSTRACTIn the skin fragility disorder epidermolysis bullosa simplex (EBS), mutations in keratin 14 (K14, also known as KRT14) or keratin 5 (K5, also known as KRT5) lead to keratinocyte rupture and skin blistering. Severe forms of EBS are associated with cytoplasmic protein aggregates, with elevated kinase activation of ERK1 and ERK2 (ERK1/2; also known as MAPK3 and MAPK1, respectively), suggesting intrinsic stress caused by misfolded keratin protein. Human keratinocyte EBS reporter cells stably expressing GFP-tagged EBS-mimetic mutant K14 were used to optimize a semi-automated system to quantify the effects of test compounds on keratin aggregates. Screening of a protein kinase inhibitor library identified several candidates that reduced aggregates and impacted on epidermal growth factor receptor (EGFR) signalling. EGF ligand exposure induced keratin aggregates in EBS reporter keratinocytes, which was reversible by EGFR inhibition. EBS keratinocytes treated with a known EGFR inhibitor, afatinib, were driven out of activation and towards quiescence with minimal cell death. Aggregate reduction was accompanied by denser keratin filament networks with enhanced intercellular cohesion and resilience, which when extrapolated to a whole tissue context would predict reduced epidermal fragility in EBS patients. This assay system provides a powerful tool for discovery and development of new pathway intervention therapeutic avenues for EBS.

Slac2-b Coordinates Extracellular Vesicle Secretion to Regulate Keratinocyte Adhesion and Migration

Slac2-b, also known as exophilin-5, is a Rab27b effector protein with a role in exosome transport and is encoded by the EXPH5 gene. We previously described biallelic loss-of-function mutations in EXPH5 in an autosomal recessive form of epidermolysis bullosa simplex. However, how the loss of Slac2-b expression leads to skin fragility and erosions is unknown. In this study, we demonstrate that keratinocytes (KCs) isolated from two different individuals with mutations in EXPH5 have significant defects in cell‒matrix adhesion. EXPH5-mutant KCs also showed increased perinuclear accumulation and significantly reduced trafficking of CD63+ vesicles. These phenotypes were also seen in Slac2-b‒deficient KCs. This was coincident with a reduction in Rab27a protein expression in Slac2-b‒mutant KCs as well as reduced secretion of extracellular vesicles containing extracellular matrix proteins. Live imaging analysis revealed a strong correlation between CD63+ vesicle trafficking to the plasma membrane and focal adhesion dynamics. These findings support a role for Slac2-b in regulating local focal adhesion dynamics to support effective KC adhesion and provide insight into the underlying pathophysiology of inherited skin blistering.

Sporadic form of epidermolysis bullosa simplex with mottled pigmentation

Sporadic form of epidermolysis bullosa simplex with mottled pigmentation

307 Homozygous Biallelic KRT5 Mutations in Epidermolysis Bullosa Simplex, Including a Complete Human Keratin 5 “Knock-Out”, in Families with Extensive Consanguinity

Epidermolysis bullosa simplex (EBS) is usually inherited as an autosomal dominant disease due to monoallelic gain-of-function mutations in the KRT5 and KRT14 genes. Although autosomal recessive forms of EBS have been associated with mutations in at least 10 genes, recessive EBS due to homozygous biallelic KRT5 mutations has not been reported previously; it has been hypothesized that it would result in embryonic lethality. We sought the genetic causes of EBS in a cohort of EB patients by performing whole exome sequencing (WES) and using a disease-targeted next-generation sequencing (NGS) panel of 21 genes. The pathogenicity and consequences of the mutations were determined by expression profiling and at tissue and ultrastructural levels. Two pathogenic, homozygous missense variants of KRT5 in two patients with generalized EBS and a homozygous null mutation in a patient who died as a neonate from complications of EB were found. The two missense mutations disrupted keratin 5 expression on immunofluorescence microscopy, and the human “knock-out” of KRT5 showed no RNA and protein expression. Collectively, these findings identify biallelic KRT5 mutations with a phenotypic spectrum varying from mild, localized and generalized to lethal, expanding the genotypic profile of autosomal recessive EBS.

Biallelic KRT5 mutations in autosomal recessive epidermolysis bullosa simplex, including a complete human keratin 5 “knock-out”

Epidermolysis bullosa simplex (EBS) is usually inherited as an autosomal dominant disease due to monoallelic gain-of-function mutations in KRT5 or KRT14. Although autosomal recessive forms of EBS have been associated with mutations in at least 10 genes, recessive EBS due to homozygous biallelic KRT5 mutations has not been reported previously; it has been hypothesized that it would result in prenatal lethality. We sought the genetic causes of EB in a cohort of 512 distinct EB families by performing whole exome sequencing (WES) and using an EB-targeting next-generation sequencing (NGS) panel of 21 genes. The pathogenicity and consequences of the mutations were determined by expression profiling and at tissue and ultrastructural levels. Two pathogenic, homozygous missense variants of KRT5 in two patients with generalized EBS and a homozygous null mutation in a patient who died as a neonate from complications of EB were found. The two missense mutations disrupted keratin 5 expression on immunofluorescence microscopy, and the human “knock-out” of KRT5 showed no RNA and protein expression. Collectively, these findings identify biallelic KRT5 mutations with a phenotypic spectrum varying from mild, localized and generalized to perinatal lethal, expanding the genotypic profile of autosomal recessive EBS.

Pain and quality of life evaluation in patients with localized epidermolysis bullosa simplex

BackgroundA localized form of epidermolysis bullosa simplex (EBS-l) is considered one of the mildest forms of epidermolysis bullosa (EB), with blisters limited to the palms and soles. However, these lesions can be very painful. The aim of the study was to characterize pain in patients with EBS-l and evaluate its impact on quality of life (QoL). Patients were contacted via the Research Group of the French Society of Pediatric Dermatology and the association of EB patients (DEBRA France). One investigator used a standardized questionnaire that included validated scales for pain and QoL for a telephone interview.ResultsWe included 57 patients (27 children). All patients had pain: the mean pain on a 10-mm visual analog scale was >5 for most adults (90%) and children ≥8 years old (94%) when blisters were present and for most adults (73%) and about half of the children ≥ age 8 (53%) during dressing changes. Similar results were found for younger patients. Overall, 75% of patients had neuropathic pain; for 55% of children and 73% of adults, the pain had a moderate to severe impact on QOL. Only seven patients used premedication before changing dressings and seven regularly used oral treatment for chronic pain. A total of 21% and 23% of patients used non-steroidal anti-inflammatory drugs and grade 2 analgesics, respectively. These treatments were not effective for neuropathic pain. Six patients tried 5% lidocaine plasters on their feet, with good efficacy.ConclusionsEBS-l patients have frequent and severe pain with neuropathic characteristics. This pain is undertreated and affects QoL.

A novel KRT5 mutation associated with generalized severe epidermolysis bullosa simplex in a 2-year-old Chinese boy.

Mutations in keratin 5 (KRT5) or KRT14 genes are responsible for the most severe form of epidermolysis bullosa simplex (EBS), which is EBS generalized severe (EBS-gen sev). To date, only four pathogenic mutations (p.Arg165Ser and p.Lys199Asn in KRT5; p.Arg125Cys and p.Arg125His in KRT14) have been reported to be responsible for EBS-gen sev in the Chinese population. In the present study, a 2-year-old Chinese boy was clinically suspected to suffer from EBS, and thus Sanger sequencing was performed in the extracted genomic DNA samples from the patient, his parents and 100 healthy controls. A novel de novo heterozygous missense mutation c.503A>G (p.Glu168Gly) located at the N-terminal end segment of the 1A domain in KRT5 was identified by molecular analysis. In silico analysis tools were used to predict the pathogenicity of the novel missense mutation. A diagnosis of EBS-gen sev was thus confirmed according to the clinical presentations and molecular results.

A Drosophila Model of Epidermolysis Bullosa Simplex

The blistering skin disorder Epidermolysis bullosa simplex (EBS) results from dominant mutations in K5 or K14 genes, encoding the intermediate filament network of basal epidermal keratinocytes. The mechanisms governing keratin network formation and collapse due to EBS mutations remain incompletely understood. Drosophila lacks cytoplasmic intermediate filaments, providing a ‚null’ environment to examine the formation of keratin networks and determine mechanisms by which mutant keratins cause pathology. Here, we report that ubiquitous co-expression of transgenes encoding wild-type human K14 and K5 resulted in the formation of extensive keratin networks in Drosophila epithelial and non-epithelial tissues, causing no overt phenotype. Similar to mammalian cells, treatment of transgenic fly tissues with phosphatase inhibitors caused keratin network collapse, validating Drosophila as a genetic model system to investigate keratin dynamics. Co-expression of K5 and a K14R125C mutant that causes the most severe form of EBS resulted in widespread formation of EBS-like cytoplasmic keratin aggregates in epithelial and non-epithelial fly tissues. Expression of K14R125C/K5 caused semi-lethality; adult survivors developed wing blisters and were flightless due to lack of intercellular adhesion during wing heart development. This Drosophila model of EBS is valuable for the identification of pathways altered by mutant keratins and for development of EBS therapies.

Under‐recognition of acral peeling skin syndrome: 59 new cases with 15 novel mutations

Acral peeling skin syndrome (APSS) is a rare skin fragility disorder usually caused by mutations in the transglutaminase 5 gene (TGM5). We investigated the mutation spectrum of APSS in the U.K., Germany and Poland. We identified 59 children with APSS from 52 families. The phenotype was readily recognizable, with some variation in severity both within and between families. Most cases had been misdiagnosed as the localized form of epidermolysis bullosa simplex (EBS-loc). Eighteen different TGM5 mutations were identified, 15 of which were novel. Eight mutations were unique to a single family, nine each occurred in two families, while the common p.Gly113Cys mutation linked to a second missense variant p.Thr109Met occurred in 47 of the 52 families and was homozygous in 28. Most patients were of nonconsanguineous white European origin. We propose that APSS is under-reported and widely misdiagnosed as EBS-loc, with significant counselling implications as APSS is autosomal recessive while EBS-loc is dominant. We recommend screening for TGM5 mutations when EBS-loc is suspected but not confirmed by mutations in KRT5 or KRT14. Our report trebles the number of known TGM5 mutations. It provides further evidence that p.Gly113Cys is a founder mutation in the European population. This is consistent with the striking ethnic distribution of APSS in U.K., where the majority of patients are of nonconsanguineous white European origin, in contrast to the pattern of other recessive skin disorders.

Mutations inEXPH5result in autosomal recessive inherited skin fragility

Several different genes have been implicated in the pathophysiology of inherited blistering skin diseases. Recently, autosomal recessive loss-of-function mutations in EXPH5 (encoding exophilin-5, also known as Slac2-b, a protein involved in intracellular vesicle transport) were identified in a new mechanobullous disease resembling a form of epidermolysis bullosa simplex (EBS). Here, we searched for mutations in EXPH5 in a 4-year-old white boy with EBS in whom initial Sanger sequencing of known genes implicated in intraepidermal skin fragility failed to identify pathogenic mutations. Transmission electron microscopy of rubbed nonlesional patient skin revealed disruption of keratinocytes in the lower epidermis with cytolysis and acantholysis, keratin filament clumping and prominent perinuclear cytoplasmic vesicles, and provided the clue to the candidate gene pathology. Sanger sequencing of genomic DNA showed compound heterozygosity for two new mutations in EXPH5, c.1947dupC (p.Pro649fsPro*11) and c.2249C>A (p.Ser750*). Immunofluorescence microscopy of patient skin showed a complete absence of exophilin-5 labelling. This case represents the third pedigree with EXPH5 mutations resulting in inherited skin fragility. The clinical and molecular data expand genotype-phenotype correlation in this new form of EBS and demonstrate the important role of exophilin-5 in keratinocyte cell biology.

Ultrastructural study of a case of epidermolysis bullosa simplex superficialis (EBSS)

A very rare subset of Epidermolysis bullosa simplex (EBS), termed “EBS superficialis” (EBSS), has been described in two families. EBS superficialis is a rare autosomal dominant form of suprabasal EBS in which blistering arises just below the stratum corneum.The original report of EBSS was subsequently questioned by genetic analysis of one of the families that identified a mutation in a collagen gene responsible for dystrophic epidermolysis bullosa (DEB), thus implying that this entity is in fact a variant of DEB. Nonetheless, the existence of some form of EBSS can not be ruled out.We performed a transmission electron microscopy study of a skin biopsy from a 36 year old woman suspect of having EBSS. A skin biopsy was sequentially fixed in 3% glutaraldehyde in sodium cacodylate buffer 0.1M pH 7.3, osmium tetroxide in the same buffer and uranyl acetate in acetate-acetic acid buffer 0.1M pH 5. Dehydration was performed in ethanol and embedding in an Epon-Araldite mixture. Thin sections contrasted with uranyl acetate and lead cytrate were observed and photographed in a JEOL 100SX electron microscope.She had a few intact acral bullae in the neonatal period and superficial erosions and crusts in friction areas since then. Her one year-old boy, her older sister and the latter’s adolescent son had the same clinical picture. The patient does not display any symptoms expected for DEB.We found profound alterations of the structure of the outer layers of the epidermis. Degenerative changes were seen in the cells of the upper layers of the stratum spinosum. Nuclei are lost and flattened cells made mostly of compressed tonofilaments lay below a cleft that develops between the compressed cells and the granular cell layer (Fig. 1). The granular cell layer is very reduced and represented by a few damaged cells that stay attached to the stratum corneum (Fig. 2).The alterations do not seem to be related to collagen defects, and in the reported case the cleft develops in the altered upper region of the prickle-cell layer, just below the granular layer.

Epidermolysis bullosa simplex withPLECmutations: new phenotypes and new mutations

Genetic mutations in the plectin gene (PLEC) cause autosomal recessive forms of epidermolysis bullosa simplex (EBS) associated with either muscular dystrophy (EBS-MD) or pyloric atresia (EBS-PA). Phenotype-genotype analysis has suggested that EBS-MD is due mostly to genetic mutations affecting the central rod domain of plectin, and EBS-PA to mutations outside this domain. This study aimed to describe new phenotypes of patients with EBS-MD and EBS-PA, to identify novel PLEC mutations and to establish genotype-phenotype correlations. Seven patients with a suspicion of EBS linked to PLEC mutations were included. A standardized clinical questionnaire was sent to the physicians in charge of each patient. Immunofluorescence studies of skin biopsies followed by molecular analysis of PLEC were performed in all patients. We report the first case of nonlethal EBS-PA improving with age, the first multisystemic involvement in a patient with lethal EBS-PA, and the first patients with EBS-MD with involvement of either the bladder or oesophagus. Eleven novel PLEC mutations are also reported. Our results confirm that EBS-PA is linked to mutations in the distal exons 1-30 and 32 of PLEC. Long-term survival is possible, with skin improvement, but a delayed onset of MD is probable. While EBS-MD is linked to PLEC mutations in all exons, in most cases one of the mutations affects exon 31. The precocity of MD seems to be linked to the type and localization of the PLEC mutation(s), but no correlation with mucosal involvement has been found.

Epidermolysis bullosa with late‐onset muscular dystrophy and plectin deficiency

Epidermolysis bullosa associated with muscular dystrophy is a rare, autosomal recessive form of epidermolysis bullosa simplex caused by mutations in the plectin gene, PLEC1. We describe a phenotypically mild case due to compound heterozygous mutations in PLEC1 (2677_2685del and the novel mutation Q1644X). Clinical features included mild skin blistering since birth, slowly progressive and late-onset upper limb-predominant weakness, facial weakness, ptosis, incomplete ophthalmoplegia, and paroxysmal atrial fibrillation.

Efficient KRT14 Targeting and Functional Characterization of Transplanted Human Keratinocytes for the Treatment of Epidermolysis Bullosa Simplex

Inherited skin blistering conditions collectively named epidermolysis bullosa (EB) cause significant morbidity and mortality due to the compromise of the skin's barrier function, the pain of blisters, inflammation, and in some cases scaring and cancer. The simplex form of EB is usually caused by dominantly inherited mutations in KRT5 or KRT14. These mutations result in the production of proteins with dominant-negative activity that disrupt polymerization of intermediate filaments in the basal keratinocyte layer and result in a weak epidermal-dermal junction. The genome of adeno-associated virus (AAV) vectors can recombine with chromosomal sequence so that mutations can be corrected, or production of proteins with dominant-negative activity can be disrupted. We demonstrate a clinically feasible strategy for efficient targeting of the KRT14 gene in normal and EB-affected human keratinocytes. Using a gene-targeting vector with promoter trap design, targeted alteration of one allele of KRT14 occurred in 100% of transduced cells and transduction frequencies ranged from 0.1 to 0.6% of total cells. EBS patient keratinocytes with precise modifications of the mutant allele are preferentially recovered from targeted cell populations. Single epidermal stem cell clones produced histologically normal skin grafts after transplantation to athymic mice and could generate a sufficient number of cells to transplant the entire skin surface of an individual.

Epidermolysis Bullosa Simplex with Muscular Dystrophy

Epidermolysis bullosa simplex (EBS) is an inherited skin disorder characterized by separation of the epidermis from the underlying dermis, with the cleavage plane lying within the basal-cell layer of the epithelium. The major clinical subtypes of EBS have a dominant inheritance and have been associated with genetic defects in specific domains of keratins K5 and K14 that result in abnormal organization of the keratin network and cell disruption. Autosomal recessive forms of EBS associated with extracutaneous manifestations, such as muscular dystrophy (MIM 226670) or pyloric atresia (MIM 612138), have been linked to genetic mutations in the gene for plectin (PLEC). PLEC mutations have also been found in 2 families with the rare dominant Ogna form of EBS. This article reviews current knowledge on EBS.