Objective Epidermolytic nevus (EN) is a mosaic phenotype of epidermolytic ichthyosis (EI). This study reported a rare case of EN caused by mosaic mutation of KRT10 gene, and explored the genotype and phenotype of this disease. Methods Clinical data of a child with EN who was admitted to the Dermatology Diagnosis and Treatment Center in November 2024 were collected. Peripheral venous blood samples of the child and her parents were collected respectively, and skin tissue samples from the child's lesional site were obtained to extract whole-genome DNA. Next-generation sequencing was used to detect gene variations in the proband and her parents, which was verified by Sanger sequencing. Meanwhile, peripheral blood genomic DNA of 100 unrelated healthy individuals was extracted as control samples. Results The child, a 1-year-and-7-month-old female, was admitted to the Dermatology Diagnosis and Treatment Center due to "striate erythema on the trunk and limbs for more than 1 year". Genetic testing results showed that the child had a heterozygous variation of KRT10 gene c.466C>T: p.Arg156Cys in the lesional tissue (variation ratio 10.18%), while the child and her parents had no such variation in the blood, suggesting it was a de novo mosaic mutation; the guidelines of the American College of Medical Genetics and Genomics (ACMG) indicated that this locus mutation was pathogenic. No identical variation was found in 100 healthy controls. Conclusions This study confirms that KRT10 gene c.466C>T (p.Arg156Cys) is the pathogenic mutation of this case of EN, which causes the disease by affecting protein conformation and disrupting the assembly and stability of keratin intermediate filaments; the low proportion of heterozygous mutation in the child's lesional tissue and wild type in the peripheral blood suggest that the mutation is a somatic mosaic variation occurring in the late stage of embryonic development, with a low risk of multi-system involvement, but the possibility of germline mosaicismshould be vigilant.