Lethal acantholytic epidermolysis bullosa due to a novel homozygous deletion in DSP : expanding the phenotype and implications for desmoplakin function in skin and heart

Seven naturally variant loci serve as genetic modifiers of Lamc2jeb induced non-Herlitz junctional Epidermolysis Bullosa in mice

Epidermolysis Bullosa (EB) is a group of rare genetic disorders that compromise the structural integrity of the skin such that blisters and subsequent erosions occur after minor trauma. While primary genetic risk of all subforms of EB adhere to Mendelian patterns of inheritance, their clinical presentations and severities can vary greatly, implying genetic modifiers. The Lamc2jeb mouse model of non-Herlitz junctional EB (JEB-nH) demonstrated that genetic modifiers can contribute substantially to the phenotypic variability of JEB and likely other forms of EB. The innocuous changes in an 'EB related gene', Col17a1, have shown it to be a dominant modifier of Lamc2jeb. This work identifies six additional Quantitative Trait Loci (QTL) that modify disease in Lamc2jeb/jeb mice. Three QTL include other known 'EB related genes', with the strongest modifier effect mapping to a region including the epidermal hemi-desmosomal structural gene dystonin (Dst-e/Bpag1-e). Three other QTL map to intervals devoid of known EB-associated genes. Of these, one contains the nuclear receptor coactivator Ppargc1a as its primary candidate and the others contain related genes Pparg and Igf1, suggesting modifier pathways. These results, demonstrating the potent disease modifying effects of normally innocuous genetic variants, greatly expand the landscape of genetic modifiers of EB and therapeutic approaches that may be applied.

Inheritance of Monogenic Hereditary Skin Disease and Related Canine Breeds

The plasticity of the genome is an evolutionary factor in all animal species, including canines, but it can also be the origin of diseases caused by hereditary genetic mutation. Genetic changes, or mutations, that give rise to a pathology in most cases result from recessive alleles that are normally found with minority allelic frequency. The use of genetic improvement increases the consanguinity within canine breeds and, on many occasions, also increases the frequency of these recessive alleles, increasing the prevalence of these pathologies. This prevalence has been known for a long time, but mutations differ according to the canine breed. These genetic diseases, including skin diseases, or genodermatosis, which is narrowly defined as monogenic hereditary dermatosis. In this review, we focus on genodermatosis sensu estricto, i.e., monogenic, and hereditary dermatosis, in addition to the clinical features, diagnosis, pathogeny, and treatment. Specifically, this review analyzes epidermolytic and non-epidermolytic ichthyosis, junctional epidermolysis bullosa, nasal parakeratosis, mucinosis, dermoid sinus, among others, in canine breeds, such as Golden Retriever, German Pointer, Australian Shepherd, American Bulldog, Great Dane, Jack Russell Terrier, Labrador Retriever, Shar-Pei, and Rhodesian Ridgeback.

A novel desmoplakin mutation causes dilated cardiomyopathy with palmoplantar keratoderma as an early clinical sign

Background

PPKs represent a heterogeneous group of disorders with hyperkeratosis of palmar and/or plantar skin. PPK, hair shaft abnormalities, cardiomyopathy and arrhythmias can be caused by mutations in desmosomal genes, e.g. desmoplakin (DSP). PPK should trigger genetic testing to reveal mutations with possible related cardiac disease.

Objectives

To report a large multigenerational family with a novel DSP mutation associated with early‐onset PPK and adult‐onset cardiomyopathy and arrhythmias.

Methods

A custom‐designed in‐house panel of 35 PPK related genes was used to screen mutations in the index patient with focal PPK. The identified DSP mutation was verified by Sanger sequencing. DNA samples from 20 members of the large multigenerational family were sequenced for the DSP mutation. Medical records were reviewed. Clinical dermatological evaluation was performed, including light microscopy of hair samples. Cardiac evaluation included clinical examination, echocardiography, cardiac magnetic resonance imaging (CMR), electrocardiogram (ECG), Holter monitoring and laboratory tests.

Results

We identified a novel autosomal dominant truncating DSP c.2493delA p.(Glu831Aspfs*33) mutation associated with dilated cardiomyopathy (DCM) with arrhythmia susceptibility and focal PPK as an early cutaneous sign. The mutation was found in nine affected family members, but not in any unaffected members. Onset of dermatological findings preceded cardiac symptoms which were variable and occurred at adult age.

Conclusions

We report a novel truncating DSP mutation causing focal PPK with varying severity and left ventricular dilatation and ventricular extrasystoles. This finding emphasizes the importance of genetic diagnosis in patients with PPK for clinical counselling and management of cardiomyopathies and arrhythmias.

Variant NAXOS-Carvajal Syndrome with Rare Additional Features of Systemic Bulla and Brittle Nails: A Case Report and Literature Review

Skin abnormalities are often indicative of cardiovascular diseases. Such a disease entity is called cardiocutaneous syndrome; however, the details regarding the involvement of bulla and nails remain largely unclear. A 49-year-old man with systemic bulla was admitted for heart failure. His bulla had previously been diagnosed as epidermolysis bullosa, but no known gene mutations for it had been identified. He had a triad of palmoplantar keratosis, curly and fine hair, and cardiomyopathy, which are characteristic of NAXOS-Carvajal syndrome. This case highlights the fact that bulla and brittle nails can accompany NAXOS-Carvajal syndrome, showing that these extra-cardiac findings can help identify otherwise overlooked serious cardiac conditions.

Hair and skin predict cardiomyopathies: Carvajal and erythrokeratodermia cardiomyopathy syndromes

Carvajal and erythrokeratodermia cardiomyopathy syndromes (EKC) are rare, inherited cardiocutaneous disorders with potentially fatal consequences in young children. Some patients display features of congestive heart failure and rapidly deteriorate; others exhibit no evident warning signs until sudden death reveals underlying heart disease. We present two patients to illustrate the characteristic hair, skin, teeth, and nail abnormalities, which-especially when distinct from that of other family members-should prompt cardiac evaluation and genetic analysis. In this article, we discuss established treatments as well as a promising, novel therapeutic that has led to nearly complete resolution of the cutaneous and cardiac pathology in EKC syndrome.

Mutations in genes encoding desmosomal proteins: spectrum of cutaneous and extracutaneous abnormalities

The desmosome is a type of intercellular junction found in epithelial cells, cardiomyocytes and other specialized cell types. Composed of a network of transmembranous cadherins and intracellular armadillo, plakin and other proteins, desmosomes contribute to cell-cell adhesion, signalling, development and differentiation. Mutations in genes encoding desmosomal proteins result in a spectrum of erosive skin and mucosal phenotypes that also may affect hair or heart. This review summarizes the molecular pathology and phenotypes associated with desmosomal dysfunction with a focus on inherited disorders that involve the skin/hair, as well as associated extracutaneous pathologies. We reviewed the relevant literature to collate studies of pathogenic human mutations in desmosomes that have been reported over the last 25 years. Mutations in 12 different desmosome genes have been documented, with mutations in nine genes affecting the skin/mucous membranes (DSG1, DSG3, DSC2, DSC3, JUP, PKP1, DSP, CDSN, PERP) and eight resulting in hair abnormalities (DSG4, DSC2, DSC3, JUP, PKP1, DSP, CDSN, PERP). Mutations in three genes can result in cardiocutaneous syndromes (DSC2, JUP, DSP), although mutations have been described in five genes in inherited heart disorders that may lack any dermatological manifestations (DSG2, DSC2, JUP, PKP2, DSP). Understanding the diverse nature of these clinical phenotypes, as well as the desmosome gene mutation(s), has clinical value in managing and counselling patients, as well as demonstrating the biological role and activity of specific components of desmosomes in skin and other tissues.

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.

Betulin-Based Oleogel to Improve Wound Healing in Dystrophic Epidermolysis Bullosa: A Prospective Controlled Proof-of-Concept Study

Introduction

Skin fragility and recurrent wounds are hallmarks of hereditary epidermolysis bullosa (EB). Treatment options to accelerate wound healing are urgently needed. Oleogel-S10 contains a betulin-rich triterpene extract from birch bark. In this study, we tested the wound healing properties of topical Oleogel-S10 in patients with dystrophic EB.

Methods

We conducted an open, blindly evaluated, controlled, prospective phase II pilot trial in patients with dystrophic EB (EudraCT number 2010-019945-24). Healing of wounds treated with and without topical Oleogel-S10 was compared. Primary efficacy variable was faster reepithelialization as determined by 2 blinded experts. The main secondary outcome variable of the study was percentage of wound epithelialization.

Results

Twelve wound pairs of 10 patients with dystrophic EB were evaluated. In 5 of 12 cases, both blinded reviewers considered epithelialization of the intervention wounds as superior. In 3 cases, only one reviewer considered Oleogel-S10 as superior and the other one as equal to control. Measurements of wound size showed a trend towards accelerated wound healing with the intervention but without reaching statistical significance.

Conclusion

Our results indicate a potential for faster reepithelialization of wounds in patients with dystrophic EB when treated with Oleogel-S10 but larger studies are needed to confirm significance.

Cardiomyopathy in Patients With Hereditary Bullous Epidermolysis

INTRODUCTION AND OBJECTIVE

In recent decades, an association has been reported between epidermolysis bullosa (EB) and dilated cardiomyopathy (DC). DC is typically in an advanced phase when detected, leading to a poorer prognosis. Our objective was to determine the prevalence of DC in patients with EB seen in Hospital San Joan de Déu in Barcelona, Spain, between May 1986 and April 2015.

METHODS

This was a descriptive, cross-sectional chart-review study in which we recorded the type and main subtypes of EB and the presence or absence of DC.

RESULTS

Fifty-seven patients with EB were found, 19 with EB simplex, 10 with junctional EB, 27 with dystrophic EB (14 dominant dystrophic and 13 recessive dystrophic), and just 1 with Kindler syndrome. DC was detected in only 2 patients with recessive dystrophic EB. Twenty-three patients had presented factors that could have had a causal relationship with the potential onset of DC.

CONCLUSION

DC is a possible complication of EB, particularly in recessive dystrophic EB. Periodic follow-up should be performed to make an early diagnosis and start treatment.

Dominant de novo DSP mutations cause erythrokeratodermia-cardiomyopathy syndrome

Disorders of keratinization (DOK) show marked genotypic and phenotypic heterogeneity. In most cases, disease is primarily cutaneous, and further clinical evaluation is therefore rarely pursued. We have identified subjects with a novel DOK featuring erythrokeratodermia and initially-asymptomatic, progressive, potentially fatal cardiomyopathy, a finding not previously associated with erythrokeratodermia. We show that de novo missense mutations clustered tightly within a single spectrin repeat of DSP cause this novel cardio-cutaneous disorder, which we term erythrokeratodermia-cardiomyopathy (EKC) syndrome. We demonstrate that DSP mutations in our EKC syndrome subjects affect localization of desmosomal proteins and connexin 43 in the skin, and result in desmosome aggregation, widening of intercellular spaces, and lipid secretory defects. DSP encodes desmoplakin, a primary component of desmosomes, intercellular adhesion junctions most abundant in the epidermis and heart. Though mutations in DSP are known to cause other disorders, our cohort features the unique clinical finding of severe whole-body erythrokeratodermia, with distinct effects on localization of desmosomal proteins and connexin 43. These findings add a severe, previously undescribed syndrome featuring erythrokeratodermia and cardiomyopathy to the spectrum of disease caused by mutation in DSP, and identify a specific region of the protein critical to the pathobiology of EKC syndrome and to DSP function in the heart and skin.

Early-onset heart failure, alopecia, and cutaneous abnormalities associated with a novel compound heterozygous mutation in desmoplakin

Mutations in the desmosomal protein desmoplakin have been associated with various conditions affecting the skin and heart. The prototype is Carvajal syndrome, characterized by cardiomyopathy, woolly hair, palmoplantar keratoderma (PPK), and skin fragility. We report the case of a 3-year-old boy presenting with severe left-sided heart failure with a preceding history of cutaneous abnormalities including congenital alopecia, PPK, nail dystrophy, and follicular hyperkeratosis on the extensor surfaces. Genetic testing revealed a novel combination of two heterozygous mutations in the DSP gene encoding desmoplakin: R1400X and R2284X. Both are predicted to be deleterious to protein function. This case adds to our understanding of the spectrum of clinical presentations of syndromes associated with desmoplakin mutations and highlights the need for cardiac examination in patients with characteristic cutaneous findings.

Inherited epidermolysis bullosa: updated recommendations on diagnosis and classification

BACKGROUND

Several new targeted genes and clinical subtypes have been identified since publication in 2008 of the report of the last international consensus meeting on diagnosis and classification of epidermolysis bullosa (EB). As a correlate, new clinical manifestations have been seen in several subtypes previously described.

OBJECTIVE

We sought to arrive at an updated consensus on the classification of EB subtypes, based on newer data, both clinical and molecular.

RESULTS

In this latest consensus report, we introduce a new approach to classification ("onion skinning") that takes into account sequentially the major EB type present (based on identification of the level of skin cleavage), phenotypic characteristics (distribution and severity of disease activity; specific extracutaneous features; other), mode of inheritance, targeted protein and its relative expression in skin, gene involved and type(s) of mutation present, and--when possible--specific mutation(s) and their location(s).

LIMITATIONS

This classification scheme critically takes into account all published data through June 2013. Further modifications are likely in the future, as more is learned about this group of diseases.

CONCLUSION

The proposed classification scheme should be of value both to clinicians and researchers, emphasizing both clinical and molecular features of each EB subtype, and has sufficient flexibility incorporated in its structure to permit further modifications in the future.

Plakins, a versatile family of cytolinkers: roles in skin integrity and in human diseases

The plakin family consists of giant proteins involved in the cross-linking and organization of the cytoskeleton and adhesion complexes. They further modulate several fundamental biological processes, such as cell adhesion, migration, and polarization or signaling pathways. Inherited and acquired defects of plakins in humans and in animal models potentially lead to dramatic manifestations in the skin, striated muscles, and/or nervous system. These observations unequivocally demonstrate the key role of plakins in the maintenance of tissue integrity. Here we review the characteristics of the mammalian plakin members BPAG1 (bullous pemphigoid antigen 1), desmoplakin, plectin, envoplakin, epiplakin, MACF1 (microtubule-actin cross-linking factor 1), and periplakin, highlighting their role in skin homeostasis and diseases.

Molecular diagnosis of genodermatoses

The progress of molecular genetics helps clinicians to prove or exclude a suspected diagnosis for a vast and yet increasing number of genodermatoses. This leads to precise genetic counselling, prenatal diagnosis and preimplantation genetic haplotyping for many inherited skin conditions. It is also helpful in such occasions as phenocopy, late onset and incomplete penetrance, uniparental disomy, mitochondrial inheritance and pigmentary mosaicism. Molecular methods of two genodermatoses are explained in detail, i.e. genodermatoses with skin fragility and neurofibromatosis type 1.

Mutations with pathogenic potential in proteins located in or at the composite junctions of the intercalated disk connecting mammalian cardiomyocytes: a reference thesaurus for arrhythmogenic cardiomyopathies and for Naxos and Carvajal diseases

In the past decade, an avalanche of findings and reports has correlated arrhythmogenic ventricular cardiomyopathies (ARVC) and Naxos and Carvajal diseases with certain mutations in protein constituents of the special junctions connecting the polar regions (intercalated disks) of mature mammalian cardiomyocytes. These molecules, apparently together with some specific cytoskeletal proteins, are components of (or interact with) composite junctions. Composite junctions contain the amalgamated fusion products of the molecules that, in other cell types and tissues, occur in distinct separate junctions, i.e. desmosomes and adherens junctions. As the pertinent literature is still in an expanding phase and is obviously becoming important for various groups of researchers in basic cell and molecular biology, developmental biology, histology, physiology, cardiology, pathology and genetics, the relevant references so far recognized have been collected and are presented here in the following order: desmocollin-2 (Dsc2, DSC2), desmoglein-2 (Dsg2, DSG2), desmoplakin (DP, DSP), plakoglobin (PG, JUP), plakophilin-2 (Pkp2, PKP2) and some non-desmosomal proteins such as transmembrane protein 43 (TMEM43), ryanodine receptor 2 (RYR2), desmin, lamins A and C, striatin, titin and transforming growth factor-β3 (TGFβ3), followed by a collection of animal models and of reviews, commentaries, collections and comparative studies.

Novel desmoplakin mutation: juvenile biventricular cardiomyopathy with left ventricular non-compaction and acantholytic palmoplantar keratoderma

Two sons of a consanguineous marriage developed biventricular cardiomyopathy. One boy died of severe heart failure at the age of 6 years, the other was transplanted because of severe heart failure at the age of 10 years. In addition, focal palmoplantar keratoderma and woolly hair were apparent in both boys. As similar phenotypes have been described in Naxos disease and Carvajal syndrome, respectively, the genes for plakoglobin (JUP) and desmoplakin (DSP) were screened for mutations using direct genomic sequencing. A novel homozygous 2 bp deletion was identified in an alternatively spliced region of DSP. The deletion 5208_5209delAG led to a frameshift downstream of amino acid 1,736 with a premature truncation of the predominant cardiac isoform DSP-1. This novel homozygous truncating mutation in the isoform-1 specific region of the DSP C-terminus caused Carvajal syndrome comprising severe early-onset heart failure with features of non-compaction cardiomyopathy, woolly hair and an acantholytic form of palmoplantar keratoderma in our patient. Congenital hair abnormality and manifestation of the cutaneous phenotype in toddler age can help to identify children at risk for cardiac death.

Novel homozygous mutation in DSP causing skin fragility-woolly hair syndrome: report of a large family and review of the desmoplakin-related phenotypes

Desmoplakin is an important cytoskeletal linker for the function of the desmosomes. Linking desmoplakin to certain types of cardiocutaneous syndromes has been a hot topic recently. Skin fragility-woolly hair syndrome is a rare autosomal recessive disorder involving the desmosomes and is caused by mutation in the desmoplakin gene (DSP). We report five members from a large family with skin fragility-woolly hair syndrome. The index is a 14-year-old girl with palmoplantar keratoderma, woolly hair, variable alopecia, dystrophic nails, and excessive blistering to trivial mechanical trauma. No cardiac symptoms were reported. Although formal cardiac examination was not feasible, the echocardiographic evaluation of the other two affected younger siblings was normal. Homozygosity mapping and linkage analysis revealed a high LOD score region in the short arm of chromosome 6 that harbors the DSP. Full sequencing of the DSP showed a novel homozygous c.7097 G>A (p.R2366H) mutation in all affected members, and the parents were heterozygous. This is the report of the third case/family of the skin fragility-woolly hair syndrome in the literature. We also present a clinical and molecular review of various desmoplakin-related phenotypes, with emphasis on onset of cardiomyopathy. The complexity of the desmoplakin and its variable presentations warrant introducing the term 'desmoplakinopathies' to describe all the phenotypes related to defects in the desmoplakin.

Desmosomal molecules in and out of adhering junctions: normal and diseased States of epidermal, cardiac and mesenchymally derived cells

Current cell biology textbooks mention only two kinds of cell-to-cell adhering junctions coated with the cytoplasmic plaques: the desmosomes (maculae adhaerentes), anchoring intermediate-sized filaments (IFs), and the actin microfilament-anchoring adherens junctions (AJs), including both punctate (puncta adhaerentia) and elongate (fasciae adhaerentes) structures. In addition, however, a series of other junction types has been identified and characterized which contain desmosomal molecules but do not fit the definition of desmosomes. Of these special cell-cell junctions containing desmosomal glycoproteins or proteins we review the composite junctions (areae compositae) connecting the cardiomyocytes of mature mammalian hearts and their importance in relation to human arrhythmogenic cardiomyopathies. We also emphasize the various plakophilin-2-positive plaques in AJs (coniunctiones adhaerentes) connecting proliferatively active mesenchymally-derived cells, including interstitial cells of the heart and several soft tissue tumor cell types. Moreover, desmoplakin has also been recognized as a constituent of the plaques of the complexus adhaerentes connecting certain lymphatic endothelial cells. Finally, we emphasize the occurrence of the desmosomal transmembrane glycoprotein, desmoglein Dsg2, out of the context of any junction as dispersed cell surface molecules in certain types of melanoma cells and melanocytes. This broadening of our knowledge on the diversity of AJ structures indicates that it may still be too premature to close the textbook chapters on cell-cell junctions.