Genotype-phenotype spectrum and correlations in Chinese patients with keratinocytic epidermal naevus: A retrospective study of 22 cases

Background Keratinocytic epidermal naevus is characterised by hyperkeratotic lesions arranged along Blaschko's lines. So far, multiple genes have been implicated, but there is no detailed data or genotype-phenotype correlation studies of keratinocytic epidermal naevi in Chinese patients. Objective To evaluate the clinical, histopathological and genetic features, genotype-phenotype correlations of keratinocytic epidermal naevus in the Chinese population. Methods A retrospective study of patients with keratinocytic epidermal naevi referred to the Department of Dermatology, West China Hospital, in the last four years. Medical history, clinical data, histopathological characteristics, and evidence of genetic mutations were collected from 22 unrelated Chinese patients with this problem. Results The distribution of the keratinocytic epidermal naevi exhibited right-side dominance. Non-epidermolytic epidermis naevus was much more common. Eight reported missense mutations were found in this study, which were detected in five genes, including HRAS, KRT10, FGFR3, GJB2, and PIK3CA. HRAS was the most commonly affected gene (9/22, 40.91%) in this study, with the c.37G>C (6/22, 27.27%) substitution representing a possible hotspot mutation. Mutation allele loads were higher in the affected lesions than blood samples. Epidermolytic epidermal naevus was found in three patients exclusively carrying KRT10 mutations. Inflammatory epidermal naevi were caused by mutations of KRT10 and PIK3CA. Most of the mosaic mutations detected in keratinocytic epidermal naevi patients were the same as germline mutations identified in systemic diseases caused by these genes. Limitations The retrospective nature of the study. Conclusion Our findings reveal the genotype-phenotype spectrum and their correlation amongst Chinese patients with keratinocytic epidermal naevi. In addition, our data underscores the importance of genetic testing in lesional skin to help characterise and categorise keratinocytic epidermal naevi, decide on a therapeutic strategy, and offer genetic counselling and prenatal diagnosis.