Pathogenesis and clinical features of alopecia in epidermolysis bullosa: A systematic review.

BACKGROUND: Epidermolysis bullosa (EB) is a group of rare genetic skin diseases characterized by the gene mutations encoding adhesion proteins within the skin. These adhesion proteins are also present in normal hair follicles. Anecdotally, there have been reports of scalp alopecia as a complication of EB and there are scattered cases in the literature, but alopecia has generally been overlooked in severe blistering diseases because it is regarded as a cosmetic issue. Therefore, there is no consensus about the natural history and clinical manifestations of alopecia in EB to allow potential intervention. OBJECTIVES: To review the current literature detailing the pathogenesis and clinical presentations of alopecia in EB patients. METHODS: Relevant human studies were searched in Medline, PubMed, and EMBASE electronic databases up to October 2018. RESULTS: Only 15 reports detailed 29 EB patients with demographic and clinical manifestations of alopecia. Vertical biopsy sections were the most common method of alopecia diagnosis, and the most common pattern was patchy scalp alopecia (45%) followed by diffuse alopecia (41%). The most robust finding was nonspecific scarring alopecia in all dystrophic EB (DEB) patients and nonspecific nonscarring alopecia in most patients with EB simplex (EBS). CONCLUSIONS: Hair abnormalities observed in EB are of variable severity despite there being no universal validated alopecia scoring system, with alopecia occurring secondary to blistering, or in areas prone to trauma.

Keratins and epidermolysis bullosa simplex.

Keratin intermediate filaments play an important role in maintaining the integrity of the skin structure. Understanding the importance of this subject is possible with the investigation of keratin defects in epidermolysis bullosa simplex (EBS). Nowadays, in addition to clinical criteria, new molecular diagnostic methods, such as next generation sequencing, can help to distinguish the subgroups of EBS more precisely. Because the most important and most commonly occurring molecular defects in these patients are the defects of keratins 5 and14 (KRT5 and KRT14), comprehending the nature structure of these proteins and their involved processes can be very effective in understanding the pathophysiology of this disease and providing new and effective therapeutic platforms to treat it. Here, we summarized the various aspects of the presence of KRT5 and KRT14 in the epidermis, their relation to the incidence and severity of EBS phenotypes, and the processes with which these proteins can affect them.

A fixed denture for a child with epidermolysis bullosa simplex.

AIM: To report the caries treatment and delivery of a fixed denture for a 3-year-old girl with epidermolysis bullosa simplex (EBS). CASE REPORT: EBS is manifested on the skin or mucous membranes where skin separation is easily induced by trauma. Full- mouth rehabilitation under in-patient general anaesthesia was performed to the patient in conjunction with proper pre- and postoperative care. A fixed denture was fabricated and installed to replace the extracted teeth without later causing irritation on the mucosa. The prosthesis restored aesthetics and provided comfort without imposing the burden of compliance on the patient. CONCLUSION: Aided by meticulous pre- and postoperative care and oral hygiene reinforcement, comprehensive dental treatment coupled with fixed denture delivery can greatly improve the life quality and aesthetics for children with EBS.

Plectin deficiency leads to both muscular dystrophy and pyloric atresia in epidermolysis bullosa simplex.

Plectin is a cytoskeletal linker protein which has a long central rod and N- and C-terminal globular domains. Mutations in the gene encoding plectin (PLEC) cause two distinct autosomal recessive subtypes of epidermolysis bullosa: EB simplex (EBS) with muscular dystrophy (EBS-MD), and EBS with pyloric atresia (EBS-PA). Previous studies have demonstrated that loss of full-length plectin with residual expression of the rodless isoform leads to EBS-MD, whereas complete loss or marked attenuation of expression of full-length and rodless plectin underlies the more severe EBS-PA phenotype. However, muscular dystrophy has never been identified in EBS-PA, not even in the severe form of the disease. Here, we report the first case of EBS associated with both pyloric atresia and muscular dystrophy. Both of the premature termination codon-causing mutations of the proband are located within exon 32, the last exon of PLEC. Immunofluorescence and immunoblot analysis of skin samples and cultured fibroblasts from the proband revealed truncated plectin protein expression in low amounts. This study demonstrates that plectin deficiency can indeed lead to both muscular dystrophy and pyloric atresia in an individual EBS patient.

An inducible mouse model for epidermolysis bullosa simplex: implications for gene therapy.

The Dowling-Meara variant of epidermolysis bullosa simplex (EBS-DM) is a severe blistering disease inherited in an autosomal-dominant fashion. Here we report the generation of a mouse model that allows focal activation of a mutant keratin 14 allele in epidermal stem cells upon topical administration of an inducer, resulting in EBS phenotypes in treated areas. Using laser capture microdissection, we show that induced blisters healed by migration of surrounding nonphenotypic stem cells into the wound bed. This observation provides an explanation for the lack of mosaic forms of EBS-DM. In addition, we show that decreased mutant keratin 14 expression resulted in normal morphology and functions of the skin. Our results have important implications for gene therapy of EBS and other dominantly inherited diseases.

Keith R. Porter Lecture, 1996. Of mice and men: genetic disorders of the cytoskeleton.

Since the time when I was a postdoctoral fellow under the supervision of Dr. Howard Green, then at the Massachusetts Institute of Technology, I have been interested in understanding the molecular mechanisms underlying growth, differentiation, and development in the mammalian ectoderm. The ectoderm gives rise to epidermal keratinocytes and to neurons, which are the only two cell types of the body that devote most of their protein-synthesizing machinery to developing an elaborate cytoskeletal architecture composed of 10-nm intermediate filaments (IFs). Our interest is in understanding the architecture of the cytoskeleton in keratinocytes and in neurons, and in elucidating how perturbations in this architecture can lead to degenerative diseases of the skin and the nervous system. I will concentrate on the intermediate filament network of the skin and its associated genetic disorders, since this has been a long-standing interest of my laboratory at the University of Chicago.

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

BACKGROUND: A 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. RESULTS: We 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. CONCLUSIONS: EBS-l patients have frequent and severe pain with neuropathic characteristics. This pain is undertreated and affects QoL.

The "Kelch" Surprise: KLHL24, a New Player in the Pathogenesis of Skin Fragility.

A new protein, kelch-like 24, has recently been associated with a distinct subtype of epidermolysis bullosa simplex, a heterogeneous group of disorders associated with mechanical fragility of epidermal keratinocytes. All mutations involve the translation initiation codon and lead to a degradation-resistant N-terminally truncated kelch-like 24. Kelch-like 24 appears to be involved in the turnover of intermediated filaments, in particular of keratin 14, in keratinocytes.

Suspected epidermolysis bullosa simplex in a 5-week-old Nigerian: a case report.

BACKGROUND: Epidermolysis bullosa is a rare non scaring autosomal dominant disorder characterized by recurrent blistering of the skin and mucous membrane. The skin is fragile and minor rubbing may cause blistering. It's epidemiology in our environment is unknown probably because of paucity of information on the clinical presentation and management with resultant mortality within the first few months of life. METHOD: A case report of a 5-week-old female who presented with generalized blistering and denudation of the skin first noticed on the left foot at birth and a review of the literature on the subject using Medline and online search was used. She was treated at various traditional medicine homes and clinics before referral to the teaching hospital. She was managed initially for bullous pemphigus with antibiotics for proven septicaemia, and the wound infection ignorantly managed with daily sofratulle dressing alternating with closed dressings before a definitive clinical diagnosis of was made. RESULT: The patient was referred late to the tertiary centre. She was initially treated for bullous pemphigus and sepsis with antibiotics and wound dressings with poor response before the diagnosis of epidermlysis bullosa was made. The patient died from severe foot bleeding before blood could be transfused. CONCLUSION: Delay in making the right diagnosis hence the appropriate treatment even in a tertiary health is being highlighted.

Progress in epidermolysis bullosa: from eponyms to molecular genetic classification.

Epidermolysis bullosa, a clinically and genetically diverse group of heritable mechanobullous disorders characterized by skin fragility in the cutaneous basement membrane zone, has become a prototype for the recent progress in molecular genetics of genodermatoses. The different forms of epidermolysis bullosa have been linked to mutations in no less than 10 distinct genes encoding the major structural basement membrane zone proteins. This information has formed a basis for refined molecular classification with prognostic implications, improved genetic counseling, and prenatal and preimplantation genetic diagnosis.

Plectin-isoform-specific rescue of hemidesmosomal defects in plectin (-/-) keratinocytes.

The various plectin isoforms are among the major crosslinking elements of the cytoskeleton. The importance of plectin in epithelia is convincingly supported by the severe skin blistering observed in plectin-deficient humans and mice. Here, we identified plectin 1a (> 500 kDa), a full length plectin variant containing the sequence encoded by the alternative first exon 1a, as the isoform most prominently expressed in human and mouse keratinocytes. In skin sections and cultured keratinocytes, plectin 1a was shown to colocalize with hemidesmosomal structures. In contrast, a second isoform expressed in epithelia, plectin 1c, differing from 1a merely by a short N-terminal sequence, colocalized with microtubules. Expression of plectin 1a, but not of its N-terminal fragment alone, or of a third alternative full length isoform (plectin 1), restored the reduced number of hemidesmosome-like stable anchoring contacts in cultured plectin-null keratinocytes. Our results show for the first time that different isoforms of a cytolinker protein expressed in one cell type perform distinct functions. Moreover, the identification of plectin 1a as the isoform defects in which cause skin blistering in plectin-related genetic diseases, such as epidermolysis bullosa simplex MD and epidermolysis bullosa simplex Ogna, could have implications for the future development of clinical therapies for patients.

Is filaggrin really a filament-aggregating protein in vivo?

Filaggrin, a basic protein of the stratum corneum, was named as such because of its capability to aggregate keratin intermediate filaments in vitro. To investigate its filament-aggregating capability in vivo, we performed immunoelectron microscopy in three autosomal dominant genodermatoses serving as in vivo models of abnormalities of keratin filament aggregation. In bullous congenital ichthyosiform erythroderma Brocq and epidermolytic palmoplantar keratoderma Voerner suprabasal clumping of keratin filaments prevents the normal spreading of keratohyalin between keratin filaments. Keratohyalin granules, either isolated or attached to clumped keratins, were specifically labelled by the anti-filaggrin antibody, whereas tonofilament clumps did not show any reaction. In epidermolysis bullosa herpetiformis Dowling-Meara the abnormal filament aggregation occurred in basal cell keratins where no reaction of the anti-filaggrin antibody was detected. In high level keratinocytes with normal distribution of tonofilaments, normal stellate keratohyalin reacted specifically. In all instances keratin filament clumping occurred independently of, and spatially separated from, the first signs of profilaggrin synthesis and keratohyalin granule formation. Thus, in these disorders, filaggrin is not involved in filament aggregation.

[Keratin diseases]. / Keratinsygdomme.

The rapid development in human genome research has resulted in a tremendous increase in our understanding of the molecular basis of many genetic skin diseases. One outstanding example of this is diseases caused by mutations in keratin genes, which comprise several disorders of the epidermis, as for example the different types of epidermolysis bullosa simplex. In this respect, the most important questions have been to 1. Define the molecular defect. 2. Unravel the pathophysiological mechanisms that lead to the characteristic phenotype and 3. Design of new therapeutic strategies. Molecular research has contributed significantly to the first two issues whereas a therapeutic break-through has yet to appear.

Defining keratin protein function in skin epithelia: epidermolysis bullosa simplex and its aftermath.

Epidermolysis bullosa simplex (EBS) is a rare genetic condition typified by superficial bullous lesions following incident frictional trauma to the skin. Most cases of EBS are due to dominantly acting mutations in keratin 14 (K14) or K5, the type I and II intermediate filament (IF) proteins that copolymerize to form a pancytoplasmic network of 10 nm filaments in basal keratinocytes of epidermis and related epithelia. Defects in K5-K14 filament network architecture cause basal keratinocytes to become fragile, and account for their rupture upon exposure to mechanical trauma. The discovery of the etiology and pathophysiology of EBS was intimately linked to the quest for an understanding of the properties and function of keratin filaments in skin epithelia. Since then, continued cross-fertilization between basic science efforts and clinical endeavors has highlighted several additional functional roles for keratin proteins in the skin, suggested new avenues for effective therapies for keratin-based diseases, and expanded our understanding of the remarkable properties of the skin as an organ system.

Bone mineralization in children with epidermolysis bullosa.

BACKGROUND: Various factors may have deleterious effects on bone health in patients with epidermolysis bullosa (EB). OBJECTIVES: In a retrospective notes review, to assess bone mineralization in children with EB and to identify the relative contributions of nutrition, activity and disease severity to low bone mass. METHODS: Thirty-nine children with EB [32 recessive dystrophic EB (RDEB), four Dowling-Meara EB simplex (DMEBS) and three junctional EB (JEB)] had lumbar spine bone mass measured using dual X-ray absorptiometry (GE Lunar Prodigy; GE Healthcare, Chalfont St Giles, U.K.). Seventy-six healthy children were also studied. Weight and height were recorded and mobility was rated. RESULTS: Children with RDEB and JEB, but not those with DMEBS, had lower bone mineral density SD scores than controls; differences remained after adjusting for the smaller body size of the patients. Bone mass was best predicted by mobility rating. CONCLUSIONS: Children with RDEB and JEB have low bone mass after adjusting for their smaller size, which may put them at risk for fragility fractures. Low bone mass was best predicted by the level of mobility, raising the hypothesis that improving activity or bone loading may be a potential preventive intervention in these children. However, as low bone mass may be multifactorial in these children, more detailed investigation of potential aetiological factors is required before interventions are planned.