Burnlike scars: A sign suggestive of KLHL24-related epidermolysis bullosa simplex.

Epidermolysis bullosa simplex is a group of inherited disorders with allelic and locus heterogeneity in which skin fragility and blistering within the skin occur. Mutations in KRT5 and KRT14 underlie the majority of reported cases. Mutations in KLHL24, a gene that encodes KLHL24 protein, have been reported recently to cause a generalized subtype of epidermolysis bullosa simplex, presumably by increasing the degradation of keratin 14. We describe a case of KLHL24-related epidermolysis bullosa simplex and highlight the burn-like pattern of scars.

Identification of two rare and novel large deletions in ITGB4 gene causing epidermolysis bullosa with pyloric atresia.

Epidermolysis bullosa with pyloric atresia (EB-PA) is a rare autosomal recessive hereditary disease with a variable prognosis from lethal to very mild. EB-PA is classified into Simplex form (EBS-PA: OMIM #612138) and Junctional form (JEB-PA: OMIM #226730), and it is caused by mutations in ITGA6, ITGB4 and PLEC genes. We report the analysis of six patients with EB-PA, including two dizygotic twins. Skin immunofluorescence epitope mapping was performed followed by PCR and direct sequencing of the ITGB4 gene. Two of the patients presented with non-lethal EB-PA associated with missense ITGB4 gene mutations. For the other four, early postnatal demise was associated with complete lack of ß4 integrin due to a variety of ITGB4 novel mutations (2 large deletions, 1 splice-site mutation and 3 missense mutations). One of the deletions spanned 278 bp, being one of the largest reported to date for this gene. Remarkably, we also found for the first time a founder effect for one novel mutation in the ITGB4 gene. We have identified 6 novel mutations in the ITGB4 gene to be added to the mutation database. Our results reveal genotype-phenotype correlations that contribute to the molecular understanding of this heterogeneous disease, a pivotal issue for prognosis and for the development of novel evidence-based therapeutic options for EB management.

Animal models for skin blistering conditions: absence of laminin 5 causes hereditary junctional mechanobullous disease in the Belgian horse.

Recent achievements in the genetic correction of keratinocytes isolated from patients with junctional epidermolysis bullosa have paved the way to a gene therapy approach for the disease. Because gene therapy protocols require preclinical validation in animals, we have characterized spontaneous animal models of junctional epidermolysis bullosa. In this study we have elucidated the genetic basis of the hereditary junctional mechanobullous disease in the Belgian horse, a condition characterized by blistering of the skin and mouth epithelia, and exungulation (loss of the hoof). Immunofluorescence analysis associated the condition to the absent expression of the gamma2 chain of laminin 5 and designated Lamc2 as the candidate gene. Comparative analysis of the nucleotide sequence of the full-length gamma2 cDNA isolated by reverse transcription polymerase chain reaction amplification of total RNA purified from the epithelium of a junctional epidermolysis bullosa foal and a healthy control disclosed a homozygous basepair insertion (1368insC) in the affected animal. Mutation 1368insC results in a downstream premature termination codon and is predicted to cause absent expression of the laminin gamma2 polypeptide. Our results also show that: (i) the horse junctional epidermolysis bullosa genetically corresponds to the severe Herlitz form of junctional epidermolysis bullosa in man; (ii) the amino acid sequence and structure of the horse laminin gamma2 chain are virtually identical to the human counterpart; (iii) the moderate eruption of skin blisters in the affected animals with respect to the human Herlitz junctional epidermolysis bullosa patients correlates with the protection provided by hair. Our observations suggest that the affected foals are a convenient source of epithelial cells from tissues that cannot be obtained from human junctional epidermolysis bullosa patients, and imply that hairless strains of animals with recessive skin disorders would be the best models for in vivo gene therapy approaches to skin blistering diseases.

Identification of a lethal form of epidermolysis bullosa simplex associated with a homozygous genetic mutation in plectin.

Genetic mutations in plectin, a cytoskeleton linker protein expressed in a large variety of tissues including skin, muscle, and nerves, cause epidermolysis bullosa simplex with muscular dystrophy, a recessive inherited disease characterized by blistering of the skin and late onset of muscular dystrophy, and Ogna epidermolysis bullosa simplex, a rare dominant inherited form of epidermolysis bullosa simplex with no muscular involvement. Here we report a novel homozygous genetic mutation (2727del14) in the plectin gene (PLEC1) associated with a lethal form of recessive inherited epidermolysis bullosa in a consanguineous family with three affected offspring. This new clinical variant of epidermolysis bullosa is characterized by general skin blistering, aplasia cutis of the limbs, developmental complications, and rapid demise after birth. Mutation 2727del14 is the first genetic defect described in PLEC1 that disrupts the plakin domain of plectin. The severe phenotype of the patients may be linked to the role of the N-terminal domain in the function of plectin and develops the understanding of the genotype-phenotype correlations in the genodermatoses affecting the dermal-epidermal junction.

Immunofluorescence analysis of villous trophoblasts: a tool for prenatal diagnosis of inherited epidermolysis bullosa with pyloric atresia.

Genetic mutations invalidating the genes for integrin alpha6beta4 and, in some cases, plectin are associated with junctional and simplex epidermolysis bullosa with pyloric atresia (PA-JEB and PA-EBS), respectively. These recessive inherited conditions are characterized by pregnancies with fetal bullae, pyloric atresia, polyhydramnios, and neonatal mucocutaneous blistering, which often results in early postnatal demise. To date, first-trimester DNA-based prenatal diagnosis is not applicable to affected kindred carrying as yet unidentified genetic mutations. Here, we show that first-trimester chorionic villi strongly express both integrin alpha6beta4 and plectin, which persist throughout the pregnancy. Based on this observation, we implemented 25 prenatal diagnoses in kindred at risk for PA-EB by immunomapping, which identified three PA-JEB-affected fetuses and 22 healthy ones. In 19 cases, including the three PA-JEB pregnancies that were prematurely terminated, the results were confirmed by chorionic villous DNA-based tests, which also led to the identification of seven previously unreported mutations in the alpha6beta4 integrin genes. Our prediction was further sustained by the birth of 22 healthy babies. These results validate chorionic villi immunofluorescence examination as a tool for prenatal diagnosis of PA-JEB and PA-EBS and indicate that this procedure could be devised for EB with muscular dystrophy, which is also associated with genetic mutations in plectin.

Novel and recurrent mutations in the laminin-5 genes causing lethal junctional epidermolysis bullosa: molecular basis and clinical course of Herlitz disease.

Herlitz disease (H-JEB), the lethal form of junctional epidermolysis bullosa, is a rare genodermatosis presenting from birth with widespread erosions and blistering of skin and mucosae because of tissue cleavage within the epidermal basement membrane. Mutations in any of the three genes encoding the alpha3, beta3 and gamma2 chains of laminin-5 underlie this recessively inherited disorder. Here, we report the molecular basis and clinical course of H-JEB in 12 patients. Two novel nonsense mutations in the gene LAMA3 (E281X and K1299X) and a novel frame-shift mutation in the gene LAMB3 (1628insG) leading to a premature termination codon were identified by DNA sequencing and confirmed by restriction fragment length polymorphism analysis. In the four patients affected, neither the resulting truncated polypeptide chains nor assembled laminin-5 protein were detectable by immunofluorescence. Three patients were found to be heterozygous for the known hotspot mutation R635X and the recurrent mutations Q373X or 29insC in the gene LAMB3, whereas five others were homozygous for R635X. Significant variations in the disease progression and survival times between 1 and 30 months in this group of H-JEB patients emphasised the impact of modifying factors and the importance of immunostaining or mRNA assessment as parallel diagnostic methods. Interestingly, the only patients who survived for longer than 6 months were four females carrying the mutation R635X homozygously. In one of them, the clinical course may have been improved by treatment with artificial skin equivalents. These data may stimulate further investigation of genotype-phenotype correlations and facilitate mutation analysis and genetic counselling of affected families.