The molecular basis of dystrophic epidermolysis bullosa in Mexico

Background: Type VII collagen gene (COL7A1) mutations are the cause of dystrophic epidermolysis bullosa (DEB), but most mutations are specific to individual families, and there are limited data on the nature of COL7A1 mutations in certain ethnic populations. Objective: To determine the molecular basis of DEB in Hispanic Mexican patients. Methods: Patients were recruited through a newly established support group, Fundacion DEBRA Mexico. Molecular analysis was performed by polymerase chain reaction (PCR) of genomic DNA using COL7A1-specific primers, heteroduplex analysis, and direct nucleotide sequencing. Results: Fifty-nine of a possible 67 COL7A1 mutations (88%) were identified in 36 affected individuals (31 recessive, five dominant) in 21 families. Recessive mutations included six frameshift mutations, four silent glycine substitutions, and two splice-site mutations. Dominant mutations comprised a de novo glycine substitution and an internal deletion. Conclusions: This study establishes the molecular basis of DEB in a group of Mexican patients. Only two of the mutations have been identified previously in other ethnic groups; the remainder are specific to this population. These new data are helpful in facilitating the accurate diagnosis of DEB subtype, in improving genetic counseling, and in providing further insight into the pathophysiology of this mechanobullous disease.