Divya Gupta

Dermatology encompasses a broad range of conditions, ranging from single-gene disorders to common complex disorders characterised by polygenic risk factors like psoriasis and atopic dermatitis. For clinicians, understanding the genetic basis of these conditions is essential for accurate diagnosis, effective management, and appropriate genetic counselling. This article aims to revisit fundamental genetic concepts, offering a foundation to a better understanding of their application in clinical practice. It introduces the fundamental genetic terminology relevant for dermatologists, along with types of mutations, inheritance patterns, key elements of pedigree charts, and major online genetic databases, which serve as valuable resources for interpreting test results and identifying disease-associated variants. Additionally, it briefly explores the basics of genetic epidemiology, including linkage analysis, and association studies.

Genomic sequencing technologies have revolutionised the diagnostic approach to genodermatoses, facilitating precise diagnosis, offering unparalleled insights into pathogenesis, and guiding personalised treatment strategies. In this article, we provide an outline for clinical evaluation, how to choose the most suitable genetic test for different dermatological presentations and examine indications for single-gene tests, gene panels, whole exome, and whole genome sequencing. We then delve into sequencing technologies, including next-generation sequencing (NGS) and its various platforms, detailing their strengths, limitations, and clinical applications. By understanding these technologies, clinicians will be better equipped to interpret test results accurately and collaborate with genetic counsellors and laboratory experts effectively.

Extramammary Paget's disease is an intraepithelial neoplasm, usually found in areas rich in apocrine gland concentration. The clinical features, histopathology, immunohistochemistry and management details of five patients (F = 3, M = 2) have been described here. While a well-defined persistent plaque with crusting and erosion was the most common presentation, hyperpigmentation, hypopigmentation and depigmentation were also observed in two patients. Characteristic Paget's cells with cytokeratin 7 and EMA positivity were seen on histopathology examination. Authors conclude that pigmentary alterations may be under-reported in extra mammary Paget's disease in the skin of colour.