Embryonic underdevelopment of the ectoderm is seen in two syndromes: anhidrotic and hidrotic ectodermal dysplasia. Figure 11-28 shows the faulty dentition and pathognomonic facies in the more severe anhidrotic type. This syndrome, which occurs almost exclusively in boys, may include alopecia, nail dystrophy, stunted growth, and severe mental retardation. During warm weather, severe hyperthermia is the result of the absence of normal perspiration, and therapy should be aimed at regulation of environmental temperature, decreased exercise, and cool clothing. The hidrotic type affects males and females equally and is generally less severe. There is no abnormal sweating. Dystrophic nails, which may be distorted in size, shape, color, or consistency, are the hallmark of the syndrome. Patients tend to have sparse body and scalp hair. The nail dystrophy may be accompanied by severe hyperkeratosis of the palms and soles, as seen in Fig. 11-29. Topical keratolytics are of some help to affected individuals.