Epidermolysis bullosa (EB) is a major, rare disease of the skin that in extreme cases can be fatal. The symptoms of EB are life-long and include mechanically-induced blistering, chronic wounds, perturbed wound healing, pain, secondary infections, alopecia, loss of nails, scarring and fibrosis. The disease manifests with a very broad spectrum of severity and presentations. The main subtypes comprise simplex EB, junctional EB, dystrophic EB and kindler EB. To date pathogenetic variants have been recognised in >20 genes. The severe forms have a very high unmet medical need, and evidence-based therapies are urgently needed.

• Accurate diagnosis of EB is not only important for treatment, but is also a prerequisite for participation in clinical therapeutic trials.
• In addition to clinical presentation and family history, genetic analysis can be carried out on single gene if there is a clear candidate gene, or in a gene panel.
• For cases which are not possible to classify, exome sequencing can be utilised.
• All these techniques can lead to accurate diagnosis.

• As with other genetic diseases, a number of new approaches to treatment are under investigation.
• These include curative approaches (e.g. gene therapy, protein and RNA-based therapies), regenerative approaches (use of somatic cells, mesenchymal stem cells, bone marrow transplantation) and disease modifying approaches (small molecules and biologicals).
• Among these, ex vivo keratinocyte gene therapy has been used for EB for more than 13 years.
• In this technique, cultured keratinocyte stem cells, known as holoclones, generate sheets of epithelium used to restore severe skin defects.
• In a recent investigation, topical and intradermal gentamicin was shown to suppress nonsense mutations and induces type VII collagen and anchoring fibrils in EB patients.
• Gentamicin therapy may thus provide a readily available treatment for RDEB patients with nonsense mutations.

• Difference types of keratinocyte gene therapy have been investigated in EB using either a retroviral vector or gene editing with CRISPR/Cas9. [1-3]
• This latter technique has been shown to be efficient in a mouse model, and is thus a promising strategy.
• HSV-1-based gene delivery targeting keratinocytes through topical delivery is also under study.
• Another group has demonstrated that 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. [4]
• In a ground-breaking procedure, autologous transgenic keratinocyte cultures were demonstrated to have the capacity to regenerate an entire, fully functional epidermis on a seven-year-old child suffering from a devastating, life-threatening form of EB. [1]
• The proviral integration pattern was maintained in vivo and epidermal renewal did not cause any clonal selection.
• Clonal tracing showed that the human epidermis is sustained not by equipotent progenitors, but by a limited number of long-lived stem cells, detected as holoclones, that can extensively self-renew in vitro and in vivo and produce progenitors that replenish terminally differentiated keratinocytes.

• While promising, successful gene therapy has been demonstrated in only a single case to date.
• The case was well documented, but is not substitute for a clinical trial.
• In addition, even if successful, the procedure is very expensive and would require extensive hospitalisation.
• Regulatory issues are also likely to be complicated.
• Successful gene therapy will require the development of safer vectors with a low risk of oncogenic potential.
• Lastly, treatment should begin as early as possible.

• While promising, successful gene therapy has been demonstrated in only a single case to date.
• The case was well documented, but is not substitute for a clinical trial.
• In addition, even if successful, the procedure is very expensive and would require extensive hospitalisation.
• Regulatory issues are also likely to be complicated.
• Successful gene therapy will require the development of safer vectors with a low risk of oncogenic potential.
• Lastly, treatment should begin as early as possible.