[Recessive epidermolysis bullosa due to composite heterozygote mutations in the COL7A1 gene]

Abstract

Background: Dystrophic epidermolysis bullosa (DEB) is a genodermatosis characterized by various abnormalities of anchoring fibrils, composed mainly of type VII collagen, at the dermal-epidermal junction. These changes are induced by mutations in the type VII collagen gene (COL7A1).

Patients and methods: A new-born boy was diagnosed with recessive DEB on the basis of typical skin lesions composed of multiple blisters with erosions on trauma-exposed body sites, including the hands and feet and the navel. Diagnosis was confirmed by pathology examination and irregular immunofluorescence staining of type VII collagen. Genomic DNA from the patient and parents were subjected to direct sequencing for the COL7A1 gene. Two heterozygous mutations were detected in the affected child. Each parent was a carrier of one heterozygous mutation.

Discussion: Over 730 mutations of the COL7A1 gene have been identified as responsible for phenotypic polymorphism of EBD. The relatively mild phenotype seen in our patient, known as "non-Hallopeau-Siemens" or "mitis" EBD, is due to residual synthesis of collagen VII. The mutation present on the maternal allele that prevents synthesis of collagen VII is compensated by the mutation on the paternal allele, which enables more or less functional collagen VII synthesis.

Keywords: COL7A1; Composite heterozygote; Hereditary epidermolysis bullosa; Hétérozygote composite; Épidermolyse bulleuse dystrophique.