A novel de novo mutation p.Ala428Asp in KRT5 gene as a cause of localized epidermolysis bullosa simplex

Identification of novel KRT5 gene variants in two Chinese patients with sporadic form of epidermolysis bullosa simplex: A case report

Epidermolysis bullosa simplex (EBS), a rare genetic disorder characterized by fragile skin that is prone to blistering and tearing, is primarily caused by mutations in genes encoding keratin proteins, such as KRT5 and KRT14. This study aimed to identify the pathogenic gene variants responsible for the sporadic form of EBS in two Chinese patients. Blood samples were collected from patients and their parents, and next-generation sequencing (NGS) was performed for variant screening. Two novel gene variants were identified within the KRT5 gene: c.1399A>T (p.Ile467Phe) in patient 1 and c.1412G>A (p.Arg471His) in patient 2. These variants were absent in the unaffected parents and a control group of 100 healthy individuals. These two novel gene variants within the KRT5 gene may be responsible for EBS, thus improving understanding of the genetic basis of EBS.

A Novel Mutation p.L461P in KRT5 Causing Localized Epidermolysis Bullosa Simplex

Background

Epidermolysis bullosa (EB) is a rare genetic disease with widely different clinical manifestations, but the relationship between genotype and phenotype is not fully understood. In the present study, we recruited a Chinese family in which two members had been diagnosed with localized EB simplex (EBS), with clinical manifestation, including blisters and erosions on the soles of the feet since infancy.

Objective

To identify and confirm the genetic variation in a Chinese family diagnosed as localized EBS.

Methods

Our study included two patients, other healthy members of the family, and 100 normal controls. Genomic DNA samples were isolated from each participant, and then polymerase chain reaction (PCR) direct sequencing was performed.

Results

The results of PCR direct sequencing revealed a novel heterozygous missense mutation in codon 461 of exon 7 of KRT5 (c.1382T>C), which led to an amino acid change (p.L461P) in the patients with EBS but was absent in unaffected family members and 100 unrelated control samples.

Conclusion

The present study broadens the mutational spectrum of EBS, and this knowledge could be harnessed for prenatal screening, gene diagnosis, and gene therapy for localized EBS.

Severe epidermolysis bullosa simplex phenotype caused by codominant mutations p.Ile377Thr in keratin 14 and p.Gly138Glu in keratin 5

Epidermolysis bullosa simplex (EBS) is a rare skin disease usually inherited in an autosomal dominant pattern. EBS is resulting from mutations in keratin 5 (KRT5) and keratin 14 (KRT14) genes encoding the keratins 5 and 14 proteins expressed in the keratinocytes of the basal layer of the epidermis. To date, seven pathogenic mutations have been reported to be responsible for EBS in the Canadian population from the province of Quebec: p.Pro25Leu, p.Leu150Pro, p.Met327Thr and p.Arg559X in KRT5; p.Arg125Ser, p.Ile377Thr and p.Ile412Phe in KRT14. Here, we present a novel French-Canadian patient diagnosed with EBS confined to the soles but presenting a severe complication form including blisters, hyperkeratosis, skin erosions and toenail abnormalities. Mutation screening was performed by direct sequencing of the entire coding regions of KRT5 and KRT14 genes and revealed the previously reported missense heterozygous mutation c. 1130T > C in KRT14 (p.Ile377Thr). Furthermore, this patient is carrying a second mutation in KRT5, c.413G > A (p.Gly138Glu), which has been linked to an increased risk of basal cell carcinoma in the literature. We suspect an impact of the p.Gly138Glu variant on the EBS phenotype severity of the studied patient. The pathogenicity and consequences of both genetic variations were simulated by in silico tools.