Monoallelic Large Intragenic KRT5 Deletions Account for Genetically Unsolved Cases of Epidermolysis Bullosa Simplex

Genotype and phenotype correlations in 441 patients with epidermolysis bullosa from China

BACKGROUND

Epidermolysis bullosa (EB) is a heterogeneous group of rare and incurable genetic blistering disorders.

OBJECTIVES

The objective was to analyse the genotype-phenotype correlation in EB among Chinese individuals.

METHODS

Next-generation sequencing and Sanger sequencing were performed to genetically confirm clinically diagnosed EB. Reverse transcription-PCR and splice-site analysis were used to evaluate the consequences of splicing mutations.

RESULTS

A total of 441 cases (413 families) across 11 genes were included. EB simplex (EBS), junctional EB (JEB), dystrophic EB (DEB), Kindler EB, simplex and junctional compound EB accounted for 23.4%, 12.7%, 61.5%, 1.1% and 0.2%, respectively. In 16 probands with presumptive recessive EB, failed to find the second allele, COL7A1 (10), COL17A1 (4), LAMB3 (1) and ITGB4 (1). De novo mutations are common in dominant EB (63.8% in EBS, 27.5% in DEB) but extremely rare in recessive DEB (RDEB; 0.74%). Mosaicism is more common than presumed, with 5.4% of dominant EBS. In JEB, only 45.0% of patients with biallelic premature termination codon (PTC) mutations in laminin 332 genes died within 24 months, with a longer average survival age of 11.1 months. In JEB, unusual phenotypes are frequently observed, notably urinary tract involvement, duodenal atresia and EB nevi. In RDEB, 48.8% of cases with biallelic PTC mutations in COL7A1 exhibited a relatively mild phenotype; they are likely to develop a severe phenotype at 0-4 years old, and the PTC mutations position closer to the N-terminal, leading to earlier onset. Glycine substitution mutations in DEB have complex genotypic and phenotypic heterogeneity. The rare subtype, dominant and recessive compound DEB, consists of 1.8% of the total DEB.

CONCLUSIONS

This study reveals the general rules governing genotype-phenotype correlations, rare phenotypes and complex genotypes. Collectively, mutation analysis in different forms of EB provides the basis for improved subclassification with accurate genetic counselling and for prenatal diagnosis.

Integrated Management Strategies for Epidermolysis Bullosa: Current Insights

Epidermolysis bullosa (EB) is a group of rare genodermatoses that is characterized by skin fragility resulting from minor trauma. There are four major subtypes, namely, EB simplex, junctional EB, dystrophic EB and Kindler EB, depending upon the localization of defective protein and resulting plane of blister formation. The phenotype is heterogeneous in terms of severity and majority of them present at birth or neonatal period. Currently, the treatment is mainly supportive and requires multidisciplinary care. The complex molecular pathology creates difficulty in discovering a unified curative treatment approach. But with arduous efforts, significant progress has been made in the development of treatment strategies in the last decade. The management strategies range from targeting the underlying causative factor to symptom-relieving approaches, and include gene, mRNA, protein, cell and combination therapies. In this review, we enumerate the promising approaches that are currently under various stages of investigation to provide effective treatment for patients with EB.

Epidermolysis bullosa

Epidermolysis bullosa (EB) is an inherited, heterogeneous group of rare genetic dermatoses characterized by mucocutaneous fragility and blister formation, inducible by often minimal trauma. A broad phenotypic spectrum has been described, with potentially severe extracutaneous manifestations, morbidity and mortality. Over 30 subtypes are recognized, grouped into four major categories, based predominantly on the plane of cleavage within the skin and reflecting the underlying molecular abnormality: EB simplex, junctional EB, dystrophic EB and Kindler EB. The study of EB has led to seminal advances in our understanding of cutaneous biology. To date, pathogenetic mutations in 16 distinct genes have been implicated in EB, encoding proteins influencing cellular integrity and adhesion. Precise diagnosis is reliant on correlating clinical, electron microscopic and immunohistological features with mutational analyses. In the absence of curative treatment, multidisciplinary care is targeted towards minimizing the risk of blister formation, wound care, symptom relief and specific complications, the most feared of which - and also the leading cause of mortality - is squamous cell carcinoma. Preclinical advances in cell-based, protein replacement and gene therapies are paving the way for clinical successes with gene correction, raising hopes amongst patients and clinicians worldwide.

Consensus reclassification of inherited epidermolysis bullosa and other disorders with skin fragility

BACKGROUND

Several new genes and clinical subtypes have been identified since the publication in 2014 of the report of the last International Consensus Meeting on Epidermolysis Bullosa (EB).

OBJECTIVES

We sought to reclassify disorders with skin fragility, with a focus on EB, based on new clinical and molecular data.

METHODS

This was a consensus expert review.

RESULTS

In this latest consensus report, we introduce the concept of genetic disorders with skin fragility, of which classical EB represents the prototype. Other disorders with skin fragility, where blisters are a minor part of the clinical picture or are not seen because skin cleavage is very superficial, are classified as separate categories. These include peeling skin disorders, erosive disorders, hyperkeratotic disorders, and connective tissue disorders with skin fragility. Because of the common manifestation of skin fragility, these 'EB-related' disorders should be considered under the EB umbrella in terms of medical and socioeconomic provision of care.

CONCLUSIONS

The proposed classification scheme should be of value both to clinicians and researchers, emphasizing both clinical and genetic features of EB. What is already known about this topic? Epidermolysis bullosa (EB) is a group of genetic disorders with skin blistering. The last updated recommendations on diagnosis and classification were published in 2014. What does this study add? We introduce the concept of genetic disorders with skin fragility, of which classical EB represents the prototype. Clinical and genetic aspects, genotype-phenotype correlations, disease-modifying factors and natural history of EB are reviewed. Other disorders with skin fragility, e.g. peeling skin disorders, erosive disorders, hyperkeratotic disorders, and connective tissue disorders with skin fragility are classified as separate categories; these 'EB-related' disorders should be considered under the EB umbrella in terms of medical and socioeconomic provision of care. Linked Comment: Pope. Br J Dermatol 2020; 183:603.

Clinical practice guidelines for laboratory diagnosis of epidermolysis bullosa

Linked Comment: https://doi.org/10.1111/bjd.18377.

https://doi.org/10.1111/bjd.18829 available online

Inherited epidermolysis bullosa: New diagnostics and new clinical phenotypes

Inherited epidermolysis bullosa (EB) is a group of heterogeneous genetic disorders characterized by skin fragility. EB comprises a large spectrum of phenotypes, ranging from severe cutaneous and extracutaneous involvement caused by lack of key adhesion proteins, to mild cutaneous fragility caused by subtle molecular defects. Disease-causing variants in 20 different genes account for the genetic and allelic heterogeneity of EB. Here, we discuss the development of laboratory methods that enabled these discoveries and the clinical and molecular features of some new EB entities elucidated during the past 5-6 years.

EB2017-Progress in Epidermolysis Bullosa Research toward Treatment and Cure

Epidermolysis bullosa, a group of heritable blistering disorders, shows extensive phenotypic variability due to mutations in as many as 20 distinct genes. There is no cure for this devastating group of disorders; however, a number of preclinical developments show promise, and some approaches have already reached the stage of early clinical trials. Dystrophic Epidermolysis Bullosa Research Association (DEBRA) International, a global coalition of national patient organizations advocating on behalf of the patients and families with epidermolysis bullosa, supports research and organizes periodic scientific and clinical meetings on this disease. The most recent meeting, EB2017, was held in Salzburg in September 2017. This report summarizes some of the recent research and clinical developments that have identified promising avenues toward treatment and perhaps eventual cure, with improved quality of life for patients with epidermolysis bullosa.