Itin Peter H, Fistarol Susanna K
Department of Dermatology, Kantonsspital Aarau, Switzerland.
Am J Med Genet C Semin Med Genet. 2004 Nov 15;131C(1):45-51. doi: 10.1002/ajmg.c.30033.
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.
外胚层发育异常是一大类遗传性疾病，其特征为一个或多个外胚层结构及其附属器存在先天性缺陷，包括毛发（毛发稀少、部分或完全脱发）、指甲（营养不良、肥厚、角化异常）、牙齿（釉质缺陷或缺失）和汗腺（发育不全或发育不良）。外胚层发育异常通常并非单纯的“单层疾病”，常伴有中胚层发育异常，极少情况下还伴有内胚层发育异常。胚胎发育过程展现出独特的组织构建区域以及胚层之间特定的相互作用，当对发育至关重要的基因发生突变或表达出现其他改变时，可能导致多种外胚层发育异常。在大约200种不同的外胚层发育异常中，约30种已在分子水平进行了研究，并确定了致病基因。弗雷雷 - 马亚和皮涅罗依据临床特征进行分类，普廖洛则将分子遗传学和临床特征整合到她的分类方案中。这两种较为传统的分类方案存在的问题是，严格应用时，“外胚层发育异常”这一术语应纳入其他几组疾病，例如伴有皮肤或毛发改变的角化病或伴有相关特征的鱼鳞病。如此分类会导致疾病列表无穷无尽，对实际工作毫无用处。最近的证据表明，在协调外胚层器官发生的不同途径中存在遗传缺陷。现代分子遗传学将越来越多地阐明不同综合征的基本缺陷，并更深入地了解胚胎学的调控机制。通过这种方式，根据所涉及突变基因的功能对外胚层发育异常进行重新分类将成为可能。拉马丁最近根据在不同类型外胚层发育异常中发现的基因功能提出了一种有用的分类方法。因此，本综述将各种外胚层发育异常分为四个主要功能亚组：细胞间通讯与信号传导、黏附、转录调控和发育。
