Expanding the phenotype of hypomaturation amelogenesis imperfecta due to a novel SLC24A4 variant
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ORIGINAL ARTICLE
Expanding the phenotype of hypomaturation amelogenesis imperfecta due to a novel SLC24A4 variant Ulrike Lepperdinger 1 & Elisabeth Maurer 2 & Martina Witsch-Baumgartner 2 & Robert Stigler 3 & Johannes Zschocke 2 & Adrian Lussi 4 & Ines Kapferer-Seebacher 1 Received: 11 March 2019 / Accepted: 23 January 2020 # The Author(s) 2020
Abstract Objectives Biallelic variants in solute carrier family 24 member 4 (SLC24A4) have been previously reported to cause nonsyndromic autosomal recessive amelogenesis imperfecta (AI) of the pigmented hypomaturation type (MIM #615887). We here describe a novel variant in SLC24A4 causing mild enamel hypomaturation defects also in heterozygous individuals. Materials and methods In the present pedigree analysis, a large consanguineous Syrian family with AI of the hypomaturation type was investigated by clinical and dental evaluation, and exome and Sanger sequencing. Dental histological investigations of seven primary and two permanent teeth were performed. Results Homozygous variants in SLC24A4 (c.1604G>A; p.Gly535Asp) were identified in five individuals with brown discolorations and irregular pits and grooves of the teeth. Severe attritions, occlusal abfractions, and the radiological lack of contrast between enamel and dentin point out a mineralization defect. Histological dental investigations confirmed the clinical diagnosis of AI of the hypomaturation type. In two heterozygous individuals, a mild hypomaturation defect was present with white and light brown enamel discolorations. Conclusions This is the first report of heterozygous SLC24A4 variants causing mild hypomaturation defects, providing confirmatory evidence that the function of SLC24A4 in calcium transport has a crucial role in the maturation stage of amelogenesis. Clinical relevance The present report is expanding the clinical phenotype of SLC24A4 variants to more severe forms of amelogenesis imperfecta. An autosomal-dominant inheritance pattern with mild clinical phenotypes in heterozygotes has to be considered. Keywords SLC24A4 . Potassium-dependent sodium/calcium exchanger . NCKX4 . Enamel . Hereditary . Malformation
Introduction Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00784-020-03222-7) contains supplementary material, which is available to authorized users. * Ines Kapferer-Seebacher [email protected] 1
Department of Operative and Restorative Dentistry, Medical University of Innsbruck, Anichstraße 35, A-6020 Innsbruck, Austria
2
Division of Human Genetics, Medical University Innsbruck, Innsbruck, Austria
3
Department of Oral and Maxillofacial Surgery, Medical University Innsbruck, Innsbruck, Austria
4
Department of Operative Dentistry and Periodontology, Faculty of Dentistry, University Medical Centre, Freiburg, Germany
Dental enamel is the most highly mineralized human tissue. It consists of a crystalline calcium phosphate (hydroxyapatite) and is characterized by the almost total absence of organic matrix [1]. Congenital disorders pre
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