Epidermolytic Hyperkeratosis Type 1 with a New Heterozygous Mutation in KRT1 Gene: A Case Report

Background: Epidermolytic hyperkeratosis (EHK) formerly known as bullous ichthyosiform erythroderma, is a rare autosomal dominant inheritance condition with a prevalence ranging from 1:200,000 to 1:300,000. The underlying etiology of which is a mutation in the genes responsible for keratin proteins synthesis, primarily in KRT1 and KRT10 genes, cataloged under OMIM number 113800. The clinicopathological presentations include blistering during the neonatal period, followed by ichthyotic hyperkeratosis in childhood and adolescence. This is characterized by hallmark features such as generalized dry skin, scaling, and hyperkeratosis, and is often associated with erythroderma. EHK may present with or without palmoplantar keratoderma involvement, depending on the keratin gene variant. Case report: A 24-year-old male of Arab descent was born with diffuse skin hyperkeratotic plates featuring erythematous fissures, covering his entire body, resembling a collodion baby. His birth was full-term via cesarean section without complications, although he later developed developmental dysplasia of the hip. By the time he started primary school, he began experiencing severe thickening of the skin around his joints, reducing flexibility and leading to contractures and significant disfigurement. He is undergoing treatment with acitretin. Genetic testing using Next-Generation Sequencing (NGS) was performed to identify the responsible gene, revealing a novel heterozygous variant in the KRT1 gene (OMIM 139350), while no variant was detected in the KRT10 gene. Conclusion: EHK type 1 manifests with a new heterozygous variant in the KRT1 gene. This rare disorder, associated with variant in genes related to keratin production such as KRT1 and KRT10, results in distinctive skin features present from birth, as well as joint problems and fungal foot infections. Genetic testing has confirmed the presence of a variant in the KRT1 gene.