Acta Dermato-Venereologica 98-9CompleteContent | Page 13

873 INVESTIGATIVE REPORT Genotype–Phenotype Correlations of Dystrophic Epidermolysis Bullosa in India: Experience from a Tertiary Care Centre Vamsi K. YENAMANDRA 1 , Shamsudheen K. VELLARIKKAL 2,3 , Madhumita R. CHOWDHURY 4 , Rijith JAYARAJAN 2 , Ankit VERMA 2 , Vinod SCARIA 2,3 , Sridhar SIVASUBBU 2,3 , Subrata BASU RAY 5 , Amit K. DINDA 6 , Madhulika KABRA 4 , Vinod K. SHARMA 1 and Gomathy SETHURAMAN 1 Departments of 1 Dermatology & Venereology, 4 Pediatrics, 5 Anatomy and 6 Pathology, All India Institute of Medical Sciences, 2 CSIR-Institute of Genomics & Integrative Biology, New Delhi, and 3 Academy of Scientific and Innovative Research, Council of Scientific and Industrial Research (CSIR), New Delhi, India Recent advances in the field of genomics have seen the successful implementation of whole exome sequencing as a rapid and efficient diagnostic strategy in several genodermatoses. The aim of this study was to explore the potential of molecular studies in dystrophic epider- molysis bullosa (DEB) in India. Whole exome sequen- cing was performed using genomic DNA from each case of epidermolysis bullosa, followed by massively parallel sequencing. Resulting reads were mapped to the human reference genome hg19. Sanger sequen- cing subsequently confirmed the potentially pathoge- nic mutations. Whole exome sequencing of 18 patients with DEB from 17 unrelated Indian families revealed 20 distinct sequence variants in the COL7A1 gene in- cluding 2 widely prevalent mutations. Dominant inhe- ritance was seen in 7 patients, while 11 patients sho- wed a highly variable recessive DEB. This preliminary study using exome sequencing is clearly encouraging and will serve as the basis for future large-scale mole- cular studies to actively identify and understand DEB in the Indian population. Key words: dystrophic EB; collagen VII; whole exome sequen- cing. Accepted Mar 27, 2018; Epub ahead of print Mar 27, 2018 Acta Derm Venereol 2018; 98: 873–879. Corr: Gomathy Sethuraman, Department of Dermatology, All India In- stitute of Medical Sciences, New Delhi-110029, India. E-mail: kgsethu@ yahoo.com/[email protected] and Sridhar Sivasubbu, CSIR-Institute of Genomics & Integrative Biology, Mathura Road, New Delhi, India. E- mail: [email protected] D ystrophic epidermolysis bullosa (DEB) is a rare ge- netic skin disease characterized by trauma-induced muco-cutaneous blistering associated with scarring, milia and nail dystrophy. Depending on the mode of inheritance, DEB is categorized into dominant (DDEB) and recessive (RDEB) forms that are further divided into many sub-types based on clinical presentation. All sub- types are associated with mutations in the COL7A1 gene encoding type VII collagen, a major stabilizing molecule of the dermoepidermal junction (DEJ) (1). Despite well-characterized genetic studies from dif- ferent ethnic backgrounds, identifying several recurrent and region-specific mutations, molecular diagnosis of DEB is still challenging. This is because most patients SIGNIFICANCE Dystrophic epidermolysis bullosa is a rare and devastating genetic skin disease associated with many complications including skin cancer. In the absence of a cure, making an accurate genetic diagnosis is therapeutic in its own right to the patients and their families as it potentially bene- fits them in terms of management and counseling. To this extent, this study provides an insight into the mutational spectrum of a small group of Indian patients with dystrophic epidermolysis bullosa and also stresses the advantage of next generation DNA sequencing technologies in aiding the accurate diagnosis of patients with epidermolysis bullosa. harbour mutations that tend to be family specific, as evident from the large repertoire of variations identified across the entire COL7A1 gene, spanning 118 exons. To make it more complex, wide phenotypic heterogeneity is also observed across the different sub-types of DEB, with multiple mutations resulting in a similar phenotype, and the same mutation showing variable clinical presenta- tions, in addition to considerable inter- and intra-familial variations (2, 3). Prior to the advent of next-generation DNA sequen- cing (NGS) technologies, molecular diagnosis of DEB was based on traditional Sanger sequencing of either the hot-spot regions or the entire COL7A1 gene, requiring more than 70 primer sets; a process that is tedious, time consuming and expensive (4). Due to its high throughput nature and ability to simultaneously sequence multiple genes, NGS, especially whole exome sequencing (WES), has revolutionized the molecular approach and provided a fast and efficient diagnostic strategy in several genoder- matoses (4, 5). In view of the scarcity of, and need for, molecular studies for DEB in India, the aim of this study was to explore the potential of WES in the phenotype and genotype characterization of patients with DEB, as part of a larger effort in understanding the mutational spectrum of patients with EB in India. METHODS Study participants In this study, 18 consecutive patients (PT01–PT18) from 17 unrela- ted Indian families, clinically diagnosed with DEB, were recruited This is an open access article under the CC BY-NC license. www.medicaljournals.se/acta Journal Compilation © 2018 Acta Dermato-Venereologica. doi: 10.2340/00015555-2929 Acta Derm Venereol 2018; 98: 873–879