Two novel recessive mutations in KRT14 identified in a cohort of 21 Spanish families with epidermolysis bullosa simplex.

BACKGROUND: Basal epidermolysis bullosa simplex (EBS) is a group of blistering genodermatoses mostly caused by mutations in the keratin genes, KRT5 and KRT14. Recessive mutations represent about 5% of all EBS mutations, being common and specific in populations with high consanguinity, where affected patients show severe phenotypes. OBJECTIVES: To accomplish the first mutational analysis in patients of Spanish origin with EBS and to delineate a comprehensive genotype-phenotype correlation. METHODS: Twenty-one EBS families were analysed. Immunofluorescence mapping at the dermoepidermal junction level was performed on skin biopsies from patients. Mutation screening of the entire coding sequences of KRT5 and KRT14 in genomic DNA was assessed by polymerase chain reaction and direct sequencing. RESULTS: KRT5 or KRT14 causative mutations were identified in 18 of the 21 EBS families. A total of 14 different mutations were disclosed, of which 12 were dominant missense mutations and two truncating recessive mutations. Five of the 14 mutations were novel including three dominant in KRT5 (p.V186E, p.T321P and p.A428T) and two recessive in KRT14 (p.K116X and p.K250RfsX8). The two patients with EBS carrying homozygous recessive mutations were affected by severe phenotypes and belonged to consanguineous families. All five families with the EBS Dowling-Meara subtype carried recurrent mutations affecting the highly conserved ends of the α-helical rod domain of K5 and K14. The seven mutations associated with the localized EBS subtype were widely distributed along the KRT5 and KRT14 genes. Two families with mottled pigmentation carried the P25L mutation in KRT5, commonly associated with this subtype. CONCLUSIONS: This study further confirms the genotype-phenotype correlation established for EBS in other ethnic groups, and is the first in a Mediterranean country (excluding Israel). This study adds two novel recessive mutations to the worldwide record to date, which includes a total of 14 mutations. As in previous reports, the recessive mutations resulted in a lack of keratin K14, giving rise to a generalized and severe presentation.

The first COL7A1 mutation survey in a large Spanish dystrophic epidermolysis bullosa cohort: c.6527insC disclosed as an unusually recurrent mutation.

BACKGROUND: Dystrophic epidermolysis bullosa (DEB) is a genodermatosis caused by mutations in COL7A1. The clinical manifestations are highly variable from nail dystrophy to life-threatening blistering, making early molecular diagnosis and prognosis of utmost importance for the affected families. Mutation identification is mandatory for prenatal testing. OBJECTIVES: To conduct the first mutational analysis of COL7A1 in a Spanish cohort, to assess mutation consequences at protein/mRNA level and to establish genotype-phenotype correlations. METHODS: Forty-nine Spanish patients with DEB were studied. Antigen mapping was performed on patient skin biopsies. COL7A1 mutation screening in genomic DNA was performed by polymerase chain reaction (PCR) and direct sequencing. Mutation consequences were determined by reverse transcriptase-PCR. RESULTS: Eight patients belonged to three unrelated families with dominant DEB. Forty-one were affected with recessive DEB (RDEB). Specifically, 27 displayed the severe generalized subtype, eight the other generalized subtype and six a localized phenotype (two pretibial, three acral and one inversa). Thirty-five mutations were identified, 20 of which are novel. The pathogenic mutation c.6527insC accounted for 46.3% of Spanish RDEB alleles. A consistent genotype-phenotype correlation was established. CONCLUSIONS: Although the COL7A1 database indicates that most DEB mutations are family specific, the pathogenic mutation c.6527insC was highly recurrent in our cohort. This level of recurrence for a single genetic defect has never previously been reported for COL7A1. Our findings are essential to the clinicians caring for patients with DEB in Spain and in the large population of Spanish descendants in Latin America. They also provide geneticists a molecular clue for a priority mutation screening strategy.