We report two Hong Kong children with severe generalized epidermolysis bullosa simplex (EBS), the most severe form of EBS, without a family history of EBS. EBS is a rare genodermatosis usually inherited in an autosomal dominant fashion although rare autosomal recessive cases have been reported. Genetic studies in these patients showed that the first case was due to a novel de novo heterozygous variant, c.377T>G (NM_000526.5 (c.377T>G, p.Leu126Arg)) in the KRT14 gene and the second case was due to a rare de novo heterozygous variant c.527A>G (NM_000424.4, c.527A>G, p.Asn176Ser) in the KRT5 gene. To our knowledge, the c.377T>G variant in the KRT14 gene has not been previously reported, and the c.527A>G variant in the KRT5 gene is a rare cause of severe generalized EBS. In severe generalized EBS, infants exhibit severe symptoms at the onset; however, they tend to improve with time. A precise genetic diagnosis in these two cases aided in counseling the families concerning the prognosis in their affected children and the recurrence risk for future pregnancies.

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.