Different phenotypes in recessive dystrophic epidermolysis bullosa patients sharing the same mutation in compound heterozygosity with two novel mutations in the type VII collagen gene.

Abstract

BACKGROUND:

Dystrophic epidermolysis bullosa (DEB) is a bullous skin disease caused by mutations in the type VII collagen gene (COL7A1).

OBJECTIVE:

To elucidate the mutations shown by two patients with DEB and understand the clinical phenotypes that they displayed.

METHODS:

We have characterized two patients, one affected by the severe recessive Hallopeau-Siemens variant of DEB (HS-RDEB) and the other by a milder recessive DEB form.

RESULTS:

In both patients we identified the R2063W missense mutation. The second mutation, in the HS-RDEB patient, was a novel 344insG, leading to a premature termination codon of translation (PTC) in exon 3, while, in the other patient, it was a novel 4965C-->T transition, which creates a new donor splice site in exon 53. The effect of this anomalous splice site leads to the maturation of a 17-nucleotides-deleted mRNA containing a PTC. In addition to this aberrant transcript, a certain amount of full-length mRNA is also generated from the mutated pre-mRNA through splicing at the canonical site.

CONCLUSIONS:

In these patients therefore the severity of the phenotype depends on the second mutation. In the patient with the 344insG mutation, leading to a PTC, type VII collagen (COLVII) molecules are exclusively composed of chains containing the R2063W substitution; as a consequence, all anchoring fibrils (AF) are abnormal and the phenotype is severe. In the other patient, the 4965C-->T splicing mutation allows the synthesis of a certain quantity of normal chains and the consequent assembly of partially functional COLVII molecules and AF, thus explaining the mild phenotype.

• Authors: R Gardella, N Zoppi, G Zambruno, S Barlati, M Colombi
• Journal: The British journal of dermatology (Br J Dermatol) Vol. 147 Issue 3 Pg. 450-7 (Sep 2002) ISSN: 0007-0963 [Print] England
• PMID: 12207583 (Publication Type: Case Reports, Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Collagen Type VII

Topics

• Adolescent
• Adult
• Collagen Type VII (genetics)
• DNA Mutational Analysis
• Epidermolysis Bullosa Dystrophica (genetics, pathology)
• Female
• Genes, Recessive
• Humans
• Male
• Mutation
• Phenotype
• Skin (ultrastructure)