Ocular Manifestation in Hypohidrotic Ectodermal Dysplasia

The term ectodermal dysplasia (ED) is defined as a heterogeneous group of heritable, congenital, and rare disorders affecting several tissues of ectodermal origin, which are characterized by alterations in two or more ectodermal structures that involve the hair, teeth, nails, and sweat gland function, in association with malformations in other organs and systems [1, 2]. Pure ED is manifested by defects in ectodermal structures alone, while ED syndromes are defined by the combination of ectodermal defects in association with other anomalies. The overall prevalence of ED syndromes is unknown, but appears rare, with a presumed cumulative frequency of approximately 7/10,000 [1]. More than 170 clinically and/or genetically distinct EDs have been catalogued, and the mode of inheritance varies among the different disorders. The current classification of ED is based on clinical features (e.g., hypohidrotic or anhidrotic forms), although a genetic classification, which led to the identification of genes encoding the EDs, has been reviewed and widely used in clinical practice [1–4]. All reviewed genes were known to be responsible for ED considering their molecular and biological functions and supported a new approach to ED classification, integrating both molecular-genetic data and corresponding clinical findings. A clinical-genetic classification of ED was proposed, expanding it to other entities in which no causative genes have been identified based on the phenotype, and speculating on possible candidate genes suggested by associated “nonectodermal” features [3]. Basically, two different nosological groups were proposed, each likely to result from mutations in genes with similar function, and possibly involved in the same mechanisms of regulation of development and/or pathogenesis. This classification allows a different approach to the patient affected by any form of ED using major clinical features to guide the physician to a grouping by underlying mechanisms [3].