Prognostic implications of determining 180 kDa bullous pemphigoid antigen (BPAG2) gene/protein pathology in neonatal junctional epidermolysis bullosa

Severe osteoporosis treated with teriparatide in a patient affected by recessive epidermolysis bullosa dystrophica

In this work, we describe the clinical and instrumental results of our experience, the first reported in the literature, of the administration of teriparatide to treat severe osteoporosis secondary to epidermolysis bullosa. Already after 2 months of therapy, the patient, a 20-year-old affected by a recessive form of epidermolysis bullosa dystrophica, had less pain and a functional recovery resulting in an improved autonomy; a satisfactory increase in the densitometric values was documented.

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.

Type XVII collagen gene mutations in junctional epidermolysis bullosa and prospects for gene therapy

Non-Herlitz junctional epidermolysis bullosa (nH-JEB) is caused predominantly by mutations leading to premature stop codons on both alleles of the type XVII collagen gene (COL17A1). The analysis of mutations in this gene has provided a means of correlating genotype with phenotype of nH-JEB patients. The phenotype of nH-JEB is characterized by generalized blistering of skin and mucous membranes with atrophic scarring and nail dystrophy. Atrophic alopecia is a distinct feature of nH-JEB patients, but one that is not associated with the severity of the disease at other sites. Enamel hypoplasia and pitting of the teeth are also characteristic for nH-JEB and can be used to facilitate the correct diagnosis in children with a blistering skin disease. Analysis of the biological consequences of mutations in the COL17A1 gene has shown that most patients lack type XVII collagen mRNA due to nonsense-mediated mRNA decay. Patients with these mutations can therefore be a target for corrective gene therapy using vectors coding for full-length type XVII collagen. Proof of principle for this approach has recently been demonstrated. The analysis of naturally occurring phenomena of gene correction in the COL17A1 gene provides evidence for other mechanisms of gene correction in genetic diseases. For example, exclusion of an exon carrying a mutation can lead to a milder phenotype of nH-JEB than predicted by the original mutation. In addition, we have gained data suggesting that COL17A1 exons harbouring pathogenic mutations can also be repaired by trans-splicing, i.e. aligning corrected RNA sequences to introns in the vicinity of faulty exons in the COL17A1 premtRNA.

Michel's medium: a potential alternative to cryoprotection for tissue transport in the investigation of genetic skin disease

Michel's medium is now well established as a transport medium to maintain tissue-fixed immunoreactants prior to direct immunofluorescence and immunoelectron microscopy. This is a practical alternative to cryofixation prior to transportation when sending skin biopsies for the investigation of cutaneous immunobullous disease. In this study we have demonstrated preservation of the cutaneous basement membrane zone proteins in skin biopsies stored in Michel's medium for periods of up to 28 days - proving that Michel's medium can be used as a transport medium when sending skin biopsies for immunohistochemical studies to determine the structural and molecular deficiencies in genodermatoses such as inherited forms of epidermolysis bullosa.

Defining target antigens in linear IgA disease using skin from subjects with inherited epidermolysis bullosa as a substrate for indirect immunofluorescence microscopy

Identification of target antigens in immunobullous disorders usually involves laborious techniques such as immunoblotting and immunoprecipitation, which do not always provide conclusive data. This is particularly true of linear IgA disease (LAD) in which the target antigen has often proved difficult to identify. As an alternative means of antigen identification in five adult patients with LAD, we performed indirect immunofluorescence (IIF) microscopy on a panel of skin samples taken from subjects with different forms of inherited epidermolysis bullosa (EB). Skin samples were selected that showed a complete absence of immunostaining for a specific basement membrane zone (BMZ) molecule (type VII collagen, laminin 5 or the 180-kDa bullous pemphigoid antigen BP180). In each case, the underlying genetic mutations had been defined and shown to consist of premature termination codons on both alleles of the particular gene, resulting in total ablation of the encoded protein. Two epidermal-binding LAD sera showed BMZ fluorescence on all substrates except BP180-deficient skin, suggesting that the target antigen was BP180, or a closely related molecule. In contrast, two dermal-binding LAD sera were positive on all substrates except the type VII collagen-deficient skin, suggesting that the target antigen was likely to be type VII collagen. One LAD serum sample, which showed combined dermal and epidermal fluorescence on normal salt-split skin, was also positive on all substrates tested, suggesting a target antigen other than type VII collagen, laminin 5 or BP180. The study confirms that LAD is a heterogeneous disorder and illustrates that IIF using a panel of skin samples which lack specific BMZ molecules, taken from subjects with inherited EB, is a relatively simple and useful tool to help identify target antigens in immunobullous disorders.

Hereditary skin diseases of hemidesmosomes

Studies of hereditary blistering skin diseases (epidermolysis bullosa) and targeted gene mutation experiments in knockout mice have greatly improved our understanding of hemidesmosomes and their associated structures in the cytoskeleton and basement membrane of the skin and mucous membranes. At least 10 molecules are recruited in hemidesmosome complexes, where they interact in a complex way. Hemidesmosomes are not simple adhesion devices, but also transduce signals for cell spreading, cell proliferation and basement membrane organisation. The dynamics of a hemidesmosome raises the metaphor of a self-assembling suspension bridge which evokes activities on both sides of the river. This review summarises our current knowledge of the molecular pathology of hemidesmosomes caused by hereditary skin disease or gene targeting experiment.

Hemidesmosomal variants of epidermolysis bullosa. Mutations in the alpha6beta4 integrin and the 180-kD bullous pemphigoid antigen/type XVII collagen genes

Epidermolysis bullosa (EB), a heterogeneous group of genodermatoses, is characterized by fragility and blistering of the skin, associated with characteristic extracutaneous manifestations. Based on clinical severity, constellation of the phenotypic manifestations, and the level of tissue separation within the cutaneous basement membrane zone, EB has been divided into distinct subcategories. Traditionally, these include the simplex, junctional and dystrophic variants of EB. Recent attention has been drawn to variants of EB demonstrating tissue separation at the level of hemidesmosomes, ultrastructurally recognizable adhesion complexes within the cutaneous basement membrane zone. Clinically, these hemidesmosomal variants manifest either as generalized atrophic benign epidermolysis bullosa (GABEB), EB with pyloric atresia, or EB with late-onset muscular dystrophy. Elucidation of basement membrane zone components by molecular cloning and development of mutation detection strategies have revealed that the hemidesmosomal variants of EB result from mutations in the genes encoding the subunit polypeptides of the 180-kD bullous pemphigoid antigen/type XVII collagen, the alpha6beta4 integrin, or plectin, respectively. Collectively, these data add to the understanding of the molecular complexity of the cutaneous basement membrane zone in EB, as attested by the fact that mutations in 10 different genes can underlie different variants of EB. Elucidation of mutations in different forms of EB has direct application to genetic counseling and DNA-based prenatal testing in families with EB.