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Ectodermal dysplasias

Authors

  • Peter H. Itin,

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    • Department of Dermatology, Kantonsspital Aarau, 5001 Aarau, Switzerland.
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    • Peter H. Itin is Professor of Dermatology and chairman of the Department of Dermatology in Aarau, Switzerland. In addition he is Associate Professor at the Department of Dermatology, University of Basel. One of the main field of interest are genodermatoses. He is the clinical advisor of the Swiss group for dystrophic epidermolysis patients (DEBRA).

  • Susanna K. Fistarol

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    • Susanna K. Fistarol is a Dermatologist with a special interest in stomatology including the genetic syndromes. She is consultant in the Department of Dermatology in Aarau, Switzerland.


Abstract

Ectodermal dysplasias are a large group of heritable conditions characterized by congenital defects of one or more ectodermal structures and their appendages: hair (hypotrichosis, partial, or total alopecia), nails (dystrophic, hypertrophic, abnormally keratinized), teeth (enamel defect or absent), and sweat glands (hypoplastic or aplastic). The ectodermal dysplasias, as a rule, are not pure “one-layer diseases.” Mesodermal and, rarely, endodermal dysplasias coexist. Embryogenesis exhibits distinct tissue organizational fields and specific interactions among the germ layers that may lead to a wide range of ectodermal dysplasias when genes important for development are mutated or otherwise altered in expression. Of the approximately 200 different ectodermal dysplasias, about 30 have been studied at the molecular level with identification of the causative gene. Freire-Maia and Pinheiro used the clinical aspects for their classification, and Priolo integrated molecular genetic and clinical aspects for her scheme. Those two more historical classification schemes have the difficulty that, when applied strictly, several additional groups of diseases should be integrated within the term “ectodermal dysplasias,” e.g. keratodermas with skin or hair alterations or the ichthyoses with associated features. Such consequent classification would lead to an endless list of diseases and would be useless for the practical work. Recent evidence implicates a genetic defect in different pathways orchestrating ectodermal organogenesis. Modern molecular genetics will increasingly elucidate the basic defects of the different syndromes and yield more insight into the regulatory mechanisms of embryology. In this way, a reclassification of ectodermal dysplasias will be possible according to the function of their involved mutated genes. Lamartine recently proposed a helpful classification according to the functions of the genes discovered in different types of ectodermal dysplasias. Accordingly, the present overview categorizes the various ectodermal dysplasias into four major functional subgroups: cell–cell communication and signaling, adhesion, transcription regulation, and development. © 2004 Wiley-Liss, Inc.

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