Huriez syndrome: Additional pathogenic variants supporting allelism to SMARCAD syndrome

Huriez syndrome (HRZ, OMIM181600) is a rare genodermatosis characterized by scleroatrophic hands and feet, hypoplastic nails, palmoplantar keratoderma, and predisposition to cutaneous squamous cell carcinoma (cSCC). We report herein three HRZ families from Croatia, the Netherlands, and Germany. Deep sequencing followed by Sanger validation, confirmed the presence of germline causative SMARCAD1 heterozygous pathogenic variants. All seven HRZ patients displayed hypohidrosis, adermatoglyphia, and one patient developed cSCC at 32 years of age. Two novel monoallelic germline mutations were identified which are predicted to disrupt the first exon-intron boundary of the skin-specific SMARCAD1 isoform. On the basis of phenotypic and genotypic convergence with Adermatoglyphia (OMIM136000) and Basan syndrome (OMIM129200), our results lend credence to the notion that these three Mendelian disorders are allelic. We propose adding Huriez syndrome to the previously suggested SMARCAD syndrome designation, which was originally invoked to describe the spectrum of monogenic disorders between Adermatoglyphia and Basan syndrome.