The ectodermal dysplasias (EDs) represent a complex and highly diverse group of congenital heritable disorders affecting tissues of ectodermal origin. The main characteristics of the group, which encompasses more than 170 conditions (Irvine 2006, OMIM 2006), consist in developmental abnormalities of two or more ectodermal appendages/ structures including skin, hair, teeth, nail and sweat glands, many of which have overlapping clinical features (Irvine 2006). Other structures derived from embryonic ectoderm include the mammary gland, thyroid gland, thymus, anterior pituitary, adrenal medulla, central nervous system, external ear, melanocytes, cornea, conjunctiva, lacrimal gland and lacrimal duct. The broader definition endeavouring all ectodermal derived structures, according to a recent review (Irvine 2006), has definite benefits in that the problems encountered by many patients and families are similar regardless of the specific subtype of ED. In addition, the wide-ranging classification is also helpful as several EDs are now known to share similar genetic mechanisms (Irvine 2006).