Multigene Next-Generation Sequencing Panel Identifies Pathogenic Variants in Patients with Unknown Subtype of Epidermolysis Bullosa: Subclassification with Prognostic Implications

Purpose: Epidermolysis bullosa (EB), the prototype of heritable blistering diseases, is caused by mutations in as many as 19 distinct genes. In this study, we evaluated the molecular basis of EB in 93 families, many of them of unknown subtype. Methods: A next generation sequencing panel covering 21 EB-related genes was developed, and mutation profiles, together with clinical features, were used to classify the patients into distinct clinical categories. Results: A total of 72 pathogenic or likely pathogenic variants in 68 families were identified in 11 of the EB-associated candidate genes, most of them (75%) being homozygous consistent with considerable consanguinity in the cohort. Approximately half of the mutations (48.6%) were previously unreported. Refined analysis of the types of mutations with addition of variants of unknown significance suspected of causing clinically consistent disease in several patients allowed subclassification of patients into different subcategories of EB in 76 of 91 families, with prognostic implications. A genetically challenging case with homozygous loss-of-function pathogenic mutations in two different EB-associated genes resulting in different subtypes was identified. In addition, secondary findings included identification of known pathogenic variants in DSP associated with arrhythmogenic right ventricular cardiomyopathy. Conclusion: Utilization of next generation sequencing panel of EB-associated genes allowed diagnostic subclassification in the neonates particularly in families of unknown subtype, with prognostication of the overall long-term outcome of the disease.