The inversa type of recessive dystrophic epidermolysis bullosa is caused by specific arginine and glycine substitutions in type VII collagen.
BACKGROUND
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.


METHODS
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.


RESULTS
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.


CONCLUSIONS
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.
Department of Genetics, University Medical Center Groningen, Hanzeplein 1, PO Box 30.001, 9700 RB Groningen, The Netherlands. p.c.van.den.akker@medgen.umcg.nl
Peter C
PC
van den Akker
Jemima E
JE
Mellerio
Anna E
AE
Martinez
Lu
L
Liu
Rowdy
R
Meijer
Patricia J C
PJ
Dopping-Hepenstal
Anthonie J
AJ
van Essen
Hans
H
Scheffer
Robert M W
RM
Hofstra
John A
JA
McGrath
Marcel F
MF
Jonkman
D000293:Adolescent; D019943:Amino Acid Substitution; D001120:Arginine / Q000235:genetics*; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D024143:Collagen Type VII / Q000235:genetics* / Q000378:metabolism; D016108:Epidermolysis Bullosa Dystrophica / Q000235:genetics* / Q000503:physiopathology*; D005808:Genes, Recessive; D056726:Genetic Association Studies; D005838:Genotype; D005998:Glycine / Q000235:genetics*; D006801:Humans; D007223:Infant; D020125:Mutation, Missense; D010641:Phenotype; D012867:Skin / Q000503:physiopathology
D024143:Collagen Type VII; D001120:Arginine; D005998:Glycine