The current classification of recessive dystrophic epidermolysis bullosa (RDEB) comprises two major subtypes: 'severe generalized RDEB' (RDEB-sev gen) with early-onset, extensive, generalized blistering and scarring, complete absence of type VII collagen, and bi-allelic COL7A1 null mutations; milder 'generalized other RDEB' (RDEB-O) with reduced-to-normal type VII collagen expression, and non-null genotypes.
To search for previously unrecognized phenotype-genotype correlations in 33 Dutch RDEB families.
We analyzed extensive clinical follow-up data, available for all patients up to 19 years, detailed type VII collagen immunostaining and genotypes, and correlated clinical phenotype to molecular phenotype and genotype.
We identified 20 novel COL7A1 mutations. In 14 of 15 RDEB-sev gen patients type VII collagen was completely absent, one had strongly reduced type VII collagen, and all carried bi-allelic null mutations. Five of 11 RDEB-O patients developed pseudosyndactyly of the fingers preceded by skin atrophy and flexion contractures later in childhood and adolescence. All five had esophageal involvement and growth retardation. Type VII collagen immunostaining ranged from strongly reduced to slightly reduced in RDEB-O patients with pseudosyndactyly, whereas RDEB-O patients without pseudosyndactyly had slightly reduced to normal type VII collagen staining. There was no difference in genotypes between both groups, although we unexpectedly found bi-allelic null mutations in two of five RDEB-O patients with pseudosyndactyly.
Pseudosyndactyly occurs in approximately half of RDEB-O patients when type VII collagen is strongly reduced. The prognosis in RDEB cannot always be simply predicted from the COL7A1 genotype.
[Show abstract][Hide abstract] ABSTRACT: A 53-year-old male patient was referred for evaluation of recurrent erosions of inguinal and anogenital areas, both lower legs and the oral mucosa. In addition, almost all nails and several teeth were lacking, and the residual teeth showed enamel defects. History revealed congenital absence of skin of large parts of the lower legs and widespread blistering in early childhood. Antigen mapping showed immunoreactivity against collagen XVII, laminin 332, collagen IV and collagen VII at the epidermal side of a skin split. Molecular analysis resulted in the identification of compound heterozygous mutations in exon 3 (c.425A>G) and exon 74 (p.Arg2069Cys) of the COL7A1 gene which has been reported in one family before. We conclude that our patient suffers from recessive dystrophic epidermolysis bullosa (EB) inversa, a rare subtype of dystrophic EB first described by Gedde-Dahl. Remarkable is the relatively mild course with clinical features formerly known as Bart syndrome.
The Open Dermatology Journal 05/2010; 4(1):52-54. DOI:10.2174/1874372201004010052
[Show abstract][Hide abstract] ABSTRACT: Despite the high incidence of revertant mosaicism (35%) in patients with the genetic skin disease epidermolysis bullosa (EB) due to correcting mutations in the genes COL17A1 and LAMB3, revertant mosaicism has not been described for COL7A1 until recently. Mutations in COL7A1 are responsible for the most devastating form of EB in adults, which is characterized by cocooned "mitten" deformities of the hands. This report shows in vivo reversion of an inherited COL7A1 mutation in a patient with recessive dystrophic EB who was homozygous for the frameshift mutation COL7A1:c.6527insC,p.2176FsX337. The patient exhibited a patch of clinically healthy revertant skin on her left forearm. The second-site mutation c.6528delT, which is present in revertant keratinocytes, resulted in correction of the reading frame. As the new CCC codon codes for the same amino acid proline as the wild-type codon CCT, the revertant cells expressed wild-type type VII collagen polypeptide, leading to restoration of skin function. We hypothesize that, on careful examination, revertant mosaicism might be found to be more common in patients with type VII collagen-deficient EB. Furthermore, the revertant keratinocytes might offer the possibility to explore cell-based therapeutic strategies, by culturing in vitro and subsequently grafting as part of bioengineered dermo-epidermal substitutes on affected skin.
[Show abstract][Hide abstract] ABSTRACT: The inversa type of recessive dystrophic epidermolysis bullosa (RDEB-I) is a rare variant of dystrophic epidermolysis bullosa, characterised by blistering in the body flexures, trunk, and mucosa. The cause of this specific distribution is unknown. So far, 20 COL7A1 genotypes have been described in RDEB-I and genotype-phenotype correlations have not been studied extensively. The aim of the study was to gain more insight into the pathophysiology of this intriguing RDEB-I phenotype.
Twenty Dutch and British RDEB-I patients, and full genotypes in 18 of them, were identified. The literature on RDEB-I genotypes was reviewed and an extensive genotype-phenotype correlation study for RDEB-I was conducted.
All 20 patients had generalised blistering at birth and during early infancy. In most patients, the age of transition from generalised to inversa distribution was before the age of 4 years. A spectrum of disease severity, ranging from the mildest 'mucosal only' phenotype to the severest phenotype with limited acral involvement, was noted. The 29 genotypes of these RDEB-I patients and those reported in the literature revealed that RDEB-I is associated with specific recessive arginine and glycine substitutions in the triple helix domain of type VII collagen.
Why these specific arginine and glycine substitutions cause the inversa distribution remains unknown. It was not possible to identify clear differences in location and nature of substituting amino acids between these mutations and missense mutations causing other RDEB phenotypes. It is hypothesised that the higher skin temperature in the affected areas plays an important role in the pathophysiology of RDEB-I.
Journal of Medical Genetics 03/2011; 48(3):160-7. DOI:10.1136/jmg.2010.082230 · 6.34 Impact Factor
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