Epidermolysis bullosa. I. Molecular genetics of the junctional and hemidesmosomal variants.
BACKGROUND
Epidermolysis bullosa (EB), a group of autosomal heritable blistering diseases, is characterised by extensive phenotypic variability with considerable morbidity and mortality. EB is classified into distinct subtypes depending on the location of blistering within the cutaneous dermoepidermal basement membrane zone. Ten genes are known to harbour mutations in the major types of EB, and the level of expression of these genes within the cutaneous basement membrane zone and in extracutaneous tissues, as well as the types and combinations of the mutations, explain in general terms the phenotypic variability.


METHODS
The DebRA Molecular Diagnostics Laboratory, established in 1996 and supported in part by the patient advocacy organisation DebRA of America, has analysed over 1000 families with different forms of EB.


RESULTS
In total, 265 cases were submitted with the preliminary diagnosis of junctional or hemidesmosomal forms of EB. We found 393 mutant alleles in seven different genes, with 173 of the mutations being distinct and 71 previously unpublished.


CONCLUSIONS
These findings attest to the clinical and molecular heterogeneity of the junctional and hemidesmosomal subtypes of EB. The results also reveal exceptions to the general rules on genotype-phenotype correlations, unusual phenotypes, and surprising genetics. Collectively, mutation analysis in different forms of EB provides the basis for improved classification with prognostic implications and for prenatal and preimplantation diagnosis in families at risk for recurrence of EB.
Varki
R
R
Department of Dermatology and Cutaneous Biology, Jefferson Medical College, and the DebRA Molecular Diagnostics Laboratory, Jefferson Institute of Molecular Medicine, Thomas Jefferson University, Philadelphia, PA 19107, USA.
Sadowski
S
S
Pfendner
E
E
Uitto
J
J
D001485:Basement Membrane / Q000166:cytology; D015815:Cell Adhesion Molecules / Q000235:genetics; D004252:DNA Mutational Analysis; D016109:Epidermolysis Bullosa, Junctional / Q000235:genetics*; D022002:Hemidesmosomes / Q000235:genetics*; D006801:Humans; D009154:Mutation / Q000235:genetics*; D000097794:Kalinin
D015815:Cell Adhesion Molecules; D000097794:Kalinin