Hypohidrotic ectodermal dysplasia (HEC) is an inherited disorder characterized by abnormal development of ectodermally-derived organs including the teeth, nails, hair and sweat glands. The most common form of HED is X-linked hypohidrotic ectodermal dysplasia (XLHED), which is associated with mutations in the EDA gene.
HEC is seen primarily in males, and some sweating does occur. Most patients are male, but females may rarely show features presumably through mosaicism. In these cases, the starch iodine test may show partially absent sweating following Blaschko's lines. Other features include teeth that are markedly reduced in number (oligodontia or hypodontia), conical (tiger) teeth, a characteristic facies (saddle nose, sunken eyes, big lips), absent nipples and brittle or ridged nails.
The patient may seek help by the dermatologist for sparse scalp hair, atopic dermatitis and problems with sweating. These patient's faces all look similar. Inheritance is XLR. Life expectancy is normal.
The starch-iodine test is performed by applying yellow starch-iodine powder to the skin being studied and putting the patient in a hot environment conducive to sweating. Normal sweating turns the yellow starch-iodine a deep purple color.
Excessive heat should be avoided. Patients may carry a spray bottle or gun to douse themselves as needed when playing outdoors. Swimming is a great sport for them. All patients should see a pediatric dentist before 2 years of age as the conical teeth and other abnormalities need intervention. This will help with eating, speaking and cosmesis. Genetic counseling should be provided.
Figure 1C shows complete edentulism in the lower jaw and four peg shaped anterior teeth in the upper jaw. J Dent Res Dent Clin Dent Prospect. 2012 Summer; 6(3): 108–112.
Figure 5 shows a female carrier of X-linked hypohidrotic ectodermal dysplasia with agenesis of the lateral maxillary incisors and conical (tiger) teeth.
Head Neck Pathol. 2012 Dec; 6(4): 460–466