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We described a 5-year-old male with hypodontia, hypohidrosis, and facial dysmorphisms characterized by a depressed nasal bridge, maxillary hypoplasia, and protuberant lips. Chromosomal analysis revealed a normal 46,XY male karyotype. Due to the presence of clinical features of hypohidrotic ectodermal dysplasia (HED), the EDA gene, located at Xq12q13.1, of the patient and his family was sequenced. Analysis of the proband's sequence revealed a missense mutation (T to A transversion) in hemizygosity state at nucleotide position 158 in exon 1 of the EDA gene, which changes codon 53 from leucine to histidine, while heterozygosity at this position was detected in the slightly affected mother; moreover, this mutation was not found in the publically available Human Gene Mutation Database. To date, our findings indicate that a novel mutation in EDA is associated with X-linked HED, adding it to the repertoire of EDA mutations.

Hypohidrotic ectodermal dysplasia (HED) is the most common type of ectodermal dysplasia (ED), which encompasses a large group of syndromes that share several phenotypic features such as missing or malformed ectodermal structures, including skin, hair, sweat glands, and teeth. X-linked hypohidrotic ectodermal dysplasia (XL-HED) is associated with mutations in ectodysplasin (EDA1). Hypohidrosis due to hypoplastic sweat glands and thin, sparse hair are phenotypic features that significantly affect the daily lives of XL-HED individuals and therefore require systematic analysis. We sought to determine the quality of life of individuals with XL-HED and to quantify sweat duct and hair phenotypes using confocal imaging, pilocarpine iontophoresis, and phototrichogram analysis. Using these highly sensitive and non-invasive techniques, we demonstrated that 11/12 XL-HED individuals presented with a complete absence of sweat ducts and that none produced sweat. We determined that the thin hair phenotype observed in XL-HED was due to multiple factors, such as fewer terminal hairs with decreased thickness and slower growth rate, as well as fewer follicular units and fewer hairs per unit. The precise characterization of XL-HED phenotypes using sensitive and non-invasive techniques presented in our study will improve upon larger genotype-phenotype studies and in the assessment of future therapies in XL-HED.

Mutations within EDA1 gene, which encodes for the ectodysplasin, cause X-linked anhidrotic ectodermal dysplasia. In this study, 23 Italian patients with anhidrotic ectodermal dysplasia were analyzed for mutations in EDA1 gene. We set up a rapid protocol through denaturing high-performance liquid chromatography, followed by sequencing, that allowed the characterization of 18 mutations, 14 novel and 4 recurrent: 8 missense mutations (p.L51Q, p.H54R, p.R156H twice, p.C332F, p.D316H, p.T378M, and p.A349T), 3 in-frame deletions (p.G82_P84del, p.A179_P191del, and p.L354del), 1 gross deletion (p.G168_G265del, identified through direct sequencing and PCR), 4 altered splicing (c.949-13T > C, c.741 + 1G/T, c.793 + 4A > T, and c.924 + 1G/T), 1 nonsense (p.Y3X), and 1 synonymous mutation (c.741G > A). Moreover, structural analysis of three missense mutations shows that alteration of the electrostatic surface of the protein (p.D316N), the break of intermonomer interactions (p.A349T) and destabilization of the single monomer structure (p.T378M), may irreversibly invalidate the EDA-A1 binding properties. Our data confirm and extend the large spectrum of EDA1 mutations and provide a rapid and efficient molecular protocol for testing EDA1 mutations in EDA patients.