Previously Unreported COL7A1 Mutation in a Somali Patient with Dystrophic Epidermolysis Bullosa

Epidermolysis Bullosa: Two rare case reports of COL7A1 and EBS-GEN SEV KRT14 variants with review of literature

EPIDERMOLYSIS

Bullosa is a rare hereditary skin condition that causes blisters. Genes encoding structural proteins at or near the dermal-epidermal junction are mutated recessively or dominantly, and this is the primary cause of EB. Herein, two Chinese boys were diagnosed with the condition, each with a different variant in a gene that serves as a reference for EB genetic counseling. Skincare significantly impacted their prognosis and quality of life.

CASE PRESENTATION

Two Chinese boys, with phenotypically normal parents, have been diagnosed with distinct blister symptoms, one with Dominant Dystrophic Epidermolysis Bullosa and the other with a severe form of Epidermolysis Bullosa Simplex. The first patient had a G-to-A variant in the COL7A1 allele, at nucleotide position 6163 which was named "G2055A". The proband is heterozygous for Dystrophic Epidermolysis Bullosa due to a COL7A1 allele with a glycine substitution at the triple helix domain. A similar variant has been discovered in his mother, indicating its potential transmission to future generations. Another patient had severe Epidermolysis Bullosa Simplex with a rare c.377T > A  variant resulting in substitution of amino acid p.Leu126Arg (NM_000526.5 (c.377T > G, p.Leu126Arg) in the Keratin 14 gene. In prior literature, Keratin 14 has been associated with an excellent prognosis. However, our patient with this infrequent variant tragically died from sepsis at 21 days old. There has been a reported occurrence of the variant only once.

CONCLUSION

Our study reveals that Epidermolysis Bullosa patients with COL7A1 c.6163G > A and KRT14 c.377T>A variants have different clinical presentations, with dominant forms of Dystrophic EB having milder phenotypes than recessive ones. Thus, the better prognosis in the c.6163G > A patient. Furthermore, c.377T>A patient was more prone to infection than the patient with c.6163G>A gene variant. Genetic testing is crucial for identifying the specific variant responsible and improving treatment options.

Novel biallelic variants in COL7A1 cause recessive dystrophic epidermolysis bullosa

Background

Autosomal recessive dystrophic epidermolysis bullosa (RDEB) is an incurable and severe inherited skin disorder characterized by recurrent blistering at the sublamina densa beneath the cutaneous basement membrane. It is caused by biallelic loss‐of‐function mutation in the gene encoding type VII collagen (COL7A1). This study aimed to identify the causative variants of a Chinese RDEB patient and further provide prenatal diagnosis for the ongoing risk pregnancy of the proband's mother.

Methods

Clinical exome sequencing (CES) has been performed and an in‐house pipeline was used to conduct a phenotype‐driven data analysis. A minigene assay was used to verify the pathogenicity of a novel splice site variant in the COL7A1.

Results

Here we report two compound heterozygous variants in COL7A1, c.3867delT (p.G1290Efs*35) and c.5532+4_5532+5delAG, identified in a RDEB patient by CES. The minigene assay confirmed that thec.5532+4_5532+5delAGchange was a noncanonic splice site variant leading to in an in‐frame deletion of exon 64. Prenatal diagnosis indicated that the present pregnancy of the patient's mother was not affected.

Conclusion

Our study expands the mutation spectrum of COL7A1 and demonstrated that CES and minigene assays were efficient tools for RDEB molecular diagnoses.