Genotype-phenotype correlations on epidermolysis bullosa with congenital absence of skin: A comprehensive review.

Congenital absence of skin (CAS) is a clinical sign associated with the main types of epidermolysis bullosa (EB). Very few studies have investigated the genetic background that may influence the occurrence of this condition. Our objective was to investigate genotype-phenotype correlations on EB with CAS through a literature revision on the pathogenic variants previously reported. A total of 171 cases (49 EB simplex, EBS; 23 junctional EB, JEB; and 99 dystrophic EB, DEB), associated with 132 pathogenic variants in eight genes, were included in the genotype-phenotype analysis. In EBS, CAS showed to be a recurrent clinical sign in EBS with pyloric atresia (PA) and EBS associated with kelch-like protein 24; CAS was also described in patients with keratins 5/14 alterations, particularly involving severe phenotypes. In JEB, this is a common clinical sign in JEB with PA associated with premature termination codon variants and/or amino acid substitutions located in the extracellular domain of integrin α6ß4 genes. In DEB with CAS, missense variants occurring close to non-collagenous interruptions of the triple-helix domain of collagen VII appear to influence this condition. This study is the largest review of patients with EB and CAS and expands the spectrum of known variants on this phenomenon.

Immunological mechanisms underlying progression of chronic wounds in recessive dystrophic epidermolysis bullosa.

Hereditary epidermolysis bullosa (EB) is a mechanobullous skin fragility disorder characterized by defective epithelial adhesion, leading to mechanical stress-induced skin blistering. Based on the level of tissue separation within the dermal-epidermal junction, EB is categorized into simplex (EBS), junctional (JEB), dystrophic (DEB) and Kindler syndrome. There is no cure for EB, and painful chronic cutaneous wounds are one of the major complications in recessive (RDEB) patients. Although RDEB is considered a cutaneous disease, recent data support the underlying systemic immunological defects. Furthermore, chronic wounds are often colonized with pathogenic microbiota, leading to excessive inflammation and altered wound healing. Consequently, patients with RDEB suffer from a painful sensation of chronic, cutaneous itching/burning and an endless battle with bacterial infections. To improve their quality of life and life expectancy, it is important to prevent cutaneous infections, dampen chronic inflammation and stimulate wound healing. A clear scientific understanding of the immunological events underlying the maintenance of chronic poorly healing wounds in RDEB patients is necessary to improve disease management and better understand other wound healing disorders. In this review, we summarize current knowledge of the role of professional phagocytes, such as neutrophils, macrophages and dendritic cells, the role of T-cell-mediated immunity in lymphoid organs, and the association of microbiota with poor wound healing in RDEB. We conclude that RDEB patients have an underlying immunity defect that seems to affect antibacterial immunity.

Self-improving dystrophic epidermolysis bullosa: First report of clinical, molecular, and genetic characterization of five patients from Southeast Asia.

Self-improving dystrophic epidermolysis bullosa is a rare subtype of dystrophic epidermolysis bullosa (DEB) characterized by significant improvement in skin fragility within the first few years of life. Genetic inheritance has previously been reported as autosomal dominant or recessive with both forms harboring mutations in COL7A1. To date, there have been no reports of this rare clinical entity from various Southeast Asian ethnicities. Here, we describe the clinical and molecular features of five patients from the Southeast Asia region who presented with predominantly acral-distributed blisters and erosions in the first few days of life. Blistering resolved over several months, without appearance of new blisters. By immunofluorescence, intraepidermal retention of Type VII collagen was observed in all patient skin biopsies when investigated with antibody staining. Genetic analysis of four patients revealed pathogenic variants in COL7A1 which have not been previously reported. The clinical diagnosis in these rare patients is confirmed with molecular histology and genetic characterization.

Recessive dystrophic epidermolysis bullosa results in painful small fibre neuropathy.

Small fibres in the skin are vulnerable to damage in metabolic or toxic conditions such as diabetes mellitus or chemotherapy resulting in small fibre neuropathy and associated neuropathic pain. Whether injury to the most distal portion of sensory small fibres due to a primary dermatological disorder can cause neuropathic pain is still unclear. Recessive dystrophic epidermolysis bullosa (RDEB) is a rare condition in which mutations of proteins of the dermo-epidermal junction lead to cycles of blistering followed by regeneration of the skin. Damage is exclusive to the skin and mucous membranes, with no known direct compromise of the nervous system. It is increasingly recognized that most RDEB patients experience daily pain, the aetiology of which is unclear but may include inflammation (in the wounds), musculoskeletal (due to atrophy and retraction scars limiting movement) or neuropathic pain. In this study we investigated the incidence of neuropathic pain and examined the presence of nerve dysfunction in RDEB patients. Around three quarters of patients presented with pain of neuropathic characteristics, which had a length-dependent distribution. Quantitative sensory testing of the foot revealed striking impairments in thermal detection thresholds combined with an increased mechanical pain sensitivity and wind up ratio (temporal summation of noxious mechanical stimuli). Nerve conduction studies showed normal large fibre sensory and motor nerve conduction; however, skin biopsy showed a significant decrease in intraepidermal nerve fibre density. Autonomic nervous system testing revealed no abnormalities in heart rate and blood pressure variability however the sympathetic skin response of the foot was impaired and sweat gland innervation was reduced. We conclude that chronic cutaneous injury can lead to injury and dysfunction of the most distal part of small sensory fibres in a length-dependent distribution resulting in disabling neuropathic pain. These findings also support the use of neuropathic pain screening tools in these patients and treatment algorithms designed to target neuropathic pain.

Recessive bullous dermolysis of the newborn in preterm siblings with a missense mutation in type VII collagen.

Bullous dermolysis of the newborn is a dominant or recessive inherited subtype of dystrophic epidermolysis bullosa characterized by the tendency to spontaneously stop blistering within the first months of life. Here we report two siblings with bullous dermolysis of the newborn who were born prematurely and have a novel recessive mutation, p.Pro2259Leu, in the triple helix domain of type VII collagen. We discuss the possible relationship between genotype and prematurity and clinical manifestations in these patients.

Allogeneic blood and bone marrow cells for the treatment of severe epidermolysis bullosa: repair of the extracellular matrix.

Contrary to the prevailing professional opinion of the past few decades, recent experimental and clinical data support the fact that protein replacement therapy by allogeneic blood and marrow transplantation is not limited to freely diffusible molecules such as enzymes, but also large structural proteins such as collagens. A prime example is the cross-correction of type VII collagen deficiency in generalised severe recessive dystrophic epidermolysis bullosa, in which blood and marrow transplantation can attenuate the mucocutaneous manifestations of the disease and improve patients' quality of life. Although allogeneic blood and marrow transplantation can improve the integrity of the skin and mucous membranes, today's accomplishments are only the first steps on the long pathway to cure. Future strategies will be built on the lessons learned from these first transplant studies.

Gene therapy: pursuing restoration of dermal adhesion in recessive dystrophic epidermolysis bullosa.

The replacement of a defective gene with a fully functional copy is the goal of the most basic gene therapy. Recessive dystrophic epidermolysis bullosa (RDEB) is characterised by a lack of adhesion of the epidermis to the dermis. It is an ideal target for gene therapy as all variants of hereditary RDEB are caused by mutations in a single gene, COL7A1, coding for type VII collagen, a key component of anchoring fibrils that secure attachment of the epidermis to the dermis. RDEB is one of the most severe variants in the epidermolysis bullosa (EB) group of heritable skin diseases. Epidermolysis bullosa is defined by chronic fragility and blistering of the skin and mucous membranes due to mutations in the genes responsible for production of the basement membrane proteins. This condition has a high personal, medical and socio-economic impact. People with RDEB require a broad spectrum of medications and specialised care. Due to this being a systemic condition, most research focus is in the area of gene therapy. Recently, preclinical works have begun to show promise. They focus on the virally mediated ex vivo correction of autologous epithelium. These corrected cells are then to be expanded and grafted onto the patient following the lead of the first successful gene therapy in dermatology being a grafting of corrected tissue for junctional EB treatment. Current progress, outstanding challenges and future directions in translating these approaches in clinics are reviewed in this article.

A case of congenital pyloric atresia with dystrophic epidermolysis bullosa.

Pyloric atresia with epidermolysis bullosa (EB) dystrophica is a rare entity that may not be immediately recognized. We describe the fourth confirmed case of pyloric atresia associated with the dystrophic subtype of EB diagnosed by standard pathologic measures, and discuss the clinical disease features and recent advances in the pathophysiology.

Type VII collagen deficiency causes defective tooth enamel formation due to poor differentiation of ameloblasts.

Recessive dystrophic epidermolysis bullosa (RDEB) is caused by mutations in the gene encoding type VII collagen (COL7), a major component of anchoring fibrils in the epidermal basement membrane zone. Patients with RDEB present a low oral hygiene index and prevalent tooth abnormalities with caries. We examined the tooth enamel structure of an RDEB patient by scanning electron microscopy. It showed irregular enamel prisms, indicating structural enamel defects. To elucidate the pathomechanisms of enamel defects due to COL7 deficiency, we investigated tooth formation in Col7a1(-/-) and COL7-rescued humanized mice that we have established. The enamel from Col7a1(-/-) mice had normal surface structure. The enamel calcification and chemical composition of Col7a1(-/-) mice were similar to those of the wild type. However, transverse sections of teeth from the Col7a1(-/-) mice showed irregular enamel prisms, which were also observed in the RDEB patient. Furthermore, the Col7a1(-/-) mice teeth had poorly differentiated ameloblasts, lacking normal enamel protein-secreting Tomes' processes, and showed reduced mRNA expression of amelogenin and other enamel-related molecules. These enamel abnormalities were corrected in the COL7-rescued humanized mice expressing a human COL7A1 transgene. These findings suggest that COL7 regulates ameloblast differentiation and is essential for the formation of Tomes' processes. Collectively, COL7 deficiency is thought to disrupt epithelial-mesenchymal interactions, leading to defective ameloblast differentiation and enamel malformation in RDEB patients.

The inversa type of recessive dystrophic epidermolysis bullosa is caused by specific arginine and glycine substitutions in type VII collagen.

BACKGROUND: The inversa type of recessive dystrophic epidermolysis bullosa (RDEB-I) is a rare variant of dystrophic epidermolysis bullosa, characterised by blistering in the body flexures, trunk, and mucosa. The cause of this specific distribution is unknown. So far, 20 COL7A1 genotypes have been described in RDEB-I and genotype-phenotype correlations have not been studied extensively. The aim of the study was to gain more insight into the pathophysiology of this intriguing RDEB-I phenotype. METHODS: Twenty Dutch and British RDEB-I patients, and full genotypes in 18 of them, were identified. The literature on RDEB-I genotypes was reviewed and an extensive genotype-phenotype correlation study for RDEB-I was conducted. RESULTS: All 20 patients had generalised blistering at birth and during early infancy. In most patients, the age of transition from generalised to inversa distribution was before the age of 4 years. A spectrum of disease severity, ranging from the mildest 'mucosal only' phenotype to the severest phenotype with limited acral involvement, was noted. The 29 genotypes of these RDEB-I patients and those reported in the literature revealed that RDEB-I is associated with specific recessive arginine and glycine substitutions in the triple helix domain of type VII collagen. DISCUSSION AND CONCLUSION: Why these specific arginine and glycine substitutions cause the inversa distribution remains unknown. It was not possible to identify clear differences in location and nature of substituting amino acids between these mutations and missense mutations causing other RDEB phenotypes. It is hypothesised that the higher skin temperature in the affected areas plays an important role in the pathophysiology of RDEB-I.

A hypomorphic mouse model of dystrophic epidermolysis bullosa reveals mechanisms of disease and response to fibroblast therapy.

Dystrophic epidermolysis bullosa (DEB) is a severe skin fragility disorder associated with trauma-induced blistering, progressive soft tissue scarring, and increased risk of skin cancer. DEB is caused by mutations in type VII collagen. In this study, we describe the generation of a collagen VII hypomorphic mouse that serves as an immunocompetent animal model for DEB. These mice expressed collagen VII at about 10% of normal levels, and their phenotype closely resembled characteristics of severe human DEB, including mucocutaneous blistering, nail dystrophy, and mitten deformities of the extremities. The oral blistering experienced by these mice resulted in growth retardation, and repeated blistering led to excessive induction of tissue repair, causing TGF-beta1-mediated contractile fibrosis generated by myofibroblasts and pseudosyndactyly in the extremities. Intradermal injection of WT fibroblasts resulted in neodeposition of collagen VII and functional restoration of the dermal-epidermal junction. Treated areas were also resistant to induced frictional stress. In contrast, untreated areas of the same mouse showed dermal-epidermal separation following induced stress. These data demonstrate that fibroblast-based treatment can be used to treat DEB in a mouse model and suggest that this approach may be effective in the development of clinical therapeutic regimens for patients with DEB.

Restrictions in oral functions caused by oral manifestations of epidermolysis bullosa.

Several forms of epidermolysis bullosa (EB) present oral manifestations. Blistering of the (peri)oral mucosa affects the opening of the mouth, the mobility of the tongue and lips, thereby restricting oral functions. We describe the prevalence and characteristics of oral manifestations of EB in relation to loss of oral functions in a cross-sectional study of different types of EB patients using standardized measurement techniques. Twenty-two patients were included. The mobility of the mandible, lips and tongue was measured, the mandibular function impairment questionnaire (MFIQ) was filled out and additional questions regarding hindrance of EB during oral hygiene and intelligibility of speech (being understood) were asked in structured interviews. The median age was 11.8 yrs. Mobility of the mandible, tongue and lip was restricted, oral hygiene procedures were hindered in most patients. A data comparison was made between the recessive dystrophic EB (RDEB) and junctional EB (JEB) groups. Mandibular function was impaired in both groups but more severely in the RDEB-population. Intelligibility in both groups was almost unaffected. Restrictions in mobility of the mouth, tongue and lips are frequently present in EB patients. These are most severe in the RDEB group and support the clinical relevance of optimizing symptomatic treatment.

A case of dystrophic epidermolysis bullosa improved with etanercept for concomitant psoriatic arthritis.

Epidermolysis bullosa is a group of inherited, chronic, non-inflammatory skin disorders, and dystrophic epidermolysis bullosa (DEB) is one of the most severe variants. The role of tumour necrosis factor alpha (TNFalpha) has not been reported in the pathogenesis of DEB. A DEB case is reported that appears to have responded well to the TNFalpha inhibitor etanercept given for the treatment of concomitant psoriatic arthritis. A progressive improvement in DEB was apparent over the first 3 months of treatment and persistent good control of DEB was noted over 3 years of therapy. A correlation between DEB improvement and etanercept has not been made, but the case may provide insight into the causal mechanisms of DEB.

Patent landscape of molecular and cellular targeted therapies for recessive dystrophic epidermolysis bullosa.

INTRODUCTION: Recessive Dystrophic Epidermolysis Bullosa (RDEB) is a monogenetic inherited genodermatosis associated with deleterious mutations in the gene encoding type VII collagen (COL7A1). COL7A1 is essential for promoting attachment of the epidermis to the dermis, and its dysfunction may lead to generalized mucosal and cutaneous blistering associated to severe deformities. Currently, management of RDEB patients is limited to supportive care, being aimed at treating and preventing common complications associated with this condition. There is a great demand to develop targeted therapies for this devastating disease and RDEB research advances are currently being translated into clinical trials. AREAS COVERED: Based on the literature and patent search, the authors have grouped the RDEB targeted therapies into five categories: a) cell-based therapies; b) gene therapy; c) protein replacement therapy; d) molecular therapy based on exon skipping; and e) drug-mediated premature termination codon read-through. The patent searching strategy involved inquiring Google and USPTO patent databases to reveal companies and institutions that are active in the area of RDEB targeted therapies. EXPERT OPINION: The patent landscape related to targeted therapies for RDEB is quite heterogeneous, with each targeted therapeutic approach being associated with its own challenges in achieving robust patent protection and identifying opportunities for future development.

Successful forearm prosthesis fitting in a patient with epidermolysis bullosa dystrophica: Case report.

BACKGROUND: Epidermolysis bullosa dystrophica is a rare dermatological disease characterized by extreme skin fragility and elevated risk of developing a squamous cell carcinoma. In some cases, amputation of a limb is necessary. Case description and methods: A 37-year-old man with recessive, severe generalized epidermolysis bullosa dystrophica developed a squamous cell carcinoma on the right forearm requiring a below-elbow amputation. Preoperative advice concerning indication and level of amputation was given. Due to potential skin problems, a conventional prosthesis was not feasible. Findings and outcomes: A custom-designed adaptive prosthesis with an upper arm cuff was trialed and was well tolerated. Multiple working tools, attached with a rotation and inclination system, allowed independence and return to work. CONCLUSION: Despite multiple potential skin problems of the stump, the patient was successfully fitted with a custom-designed adaptive prosthesis. Preparation for this fitting was done by a comprehensive multidisciplinary patient-centered approach. Clinical relevance Despite severe skin fragility, a patient with epidermolysis bullosa dystrophica was successfully fitted with a custom-designed adaptive upper limb prosthesis allowing good functional outcome. This required a multidisciplinary and patient-centered approach.

Molecular therapies for inherited epidermolysis bullosa.

Inherited epidermolysis bullosa (EB) comprises rare genetic disorders characterized by formation of blisters and erosions of skin and mucous membranes after minor mechanical trauma. The molecular basis and the pathomechanisms of the main EB types have been largely deciphered in the past decades. The burden of the disease is high and quality of life strongly affected. The treatment is still symptomatic aiming to support wound healing and resolve complications. Numerous experimental therapeutic approaches for EB have been explored in the last years, most of them dedicated to dystrophic EB. Although gene and cell therapies have been already applied in patients, molecular therapies including gene editing and repurposing of small molecules are currently very attractive. Recent data on the effect of small molecules, like aminoglycosides and angiotensin receptor blockers in preclinical models for dystrophic EB are encouraging. The efficacy in patients remains to be proven in clinical trials. Therapeutic efficacy, as well as unexpected outcomes must be carefully monitored.

Long-Term Follow-Up of Amniotic Membrane Graft for the Treatment of Symblepharon in a Patient With Recessive Dystrophic Epidermolysis Bullosa.

PURPOSE: To report a case of symblepharon due to epidermolysis bullosa (EB), surgical treatment, and follow-up to 14 years. METHODS: A 17-year-old white female with recessive dystrophic EB presented with decreased vision due to extensive symblepharon OU. There was opacification and neovascularization of the cornea OU with limited motility. RESULTS: The symblepharon was surgically lysed, anterior lamellar keratectomy performed, and amniotic membrane graft transplanted to the cornea and palpebral conjunctiva, first in the OS and subsequently in the OD. Visual acuity improved from counting fingers to 20/40 in the OS and from 20/200 to 20/70 in the OD at 2 months and 6 weeks postoperatively, respectively, with minimal symblepharon, mild corneal scarring, neovascularization, and haze of OU. She recovered full ductions, but noted diplopia and had a 35 prism diopter exotropia. Symblepharon resolved after 6 months, and alignment improved to 4 prism diopter exophoria. At 14 years follow-up, visual acuity was 20/20 in the OD and 20/30 in the OS, with clear cornea, maintained on fluorometholone 0.1% one drop OU at bedtime. CONCLUSIONS: Surgical symblepharolysis, superficial lamellar keratectomy, and amniotic membrane graft transplantation were effective for our patient with recessive dystrophic EB. Her postoperative exotropia resolved over time with monitoring and convergence exercises.

Targeted Exon Skipping Restores Type VII Collagen Expression and Anchoring Fibril Formation in an In Vivo RDEB Model.

Dystrophic epidermolysis bullosa is a group of orphan genetic skin diseases dominantly or recessively inherited, caused by mutations in COL7A1 encoding type VII collagen, which forms anchoring fibrils. Individuals with recessive dystrophic epidermolysis bullosa develop severe skin and mucosal blistering after mild trauma. The exon skipping strategy consists of modulating splicing of a pre-mRNA to induce skipping of a mutated exon. We have targeted COL7A1 exons 73 and 80, which carry recurrent mutations and whose excision preserves the open reading frame. We first showed the dispensability of these exons for type VII collagen function in vivo. We then showed that transfection of primary recessive dystrophic epidermolysis bullosa keratinocytes and fibroblasts carrying null mutations in exon 73 and/or 80, with 2'-O-methyl antisense oligoribonucleotides, led to efficient ex vivo skipping of these exons (50-95%) and resulted in a significant level (up to 36%) of type VII collagen re-expression. Finally, one or two subcutaneous injections of antisense oligoribonucleotides at doses ranging from 400 µg up to 1 mg restored type VII collagen expression and anchoring fibril formation in vivo in a xenograft model of recessive dystrophic epidermolysis bullosa skin equivalent. This work provides a proof of principle for the treatment of patients with recessive dystrophic epidermolysis bullosa by exon skipping using subcutaneous administration of antisense oligoribonucleotides.

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.