X-linked Hypohidrotic Ectodermal Dysplasia
What is X-linked Hypohidrotic Ectodermal Dysplasia?
X-linked Hypohidrotic Ectodermal Dysplasia, or XLHED, is a condition characterized by three main features:
- Lack or diminished sweat function (hypohidrosis)
- Missing and misshapen teeth (hypodontia)
- Sparse and thin hair (hypotrichosis).
XLHED is part of a group of conditions called Hypohidrotic Ectodermal Dysplasias or HEDs. The features of this condition occur because the ectoderm layer (outer-most layer of the developing embryo) does not form properly. The ectoderm forms the hair, teeth, nails, and sweat glands. When the ectoderm does not form properly, this causes: reduced or absent sweat glands (hypohidrosis); sparse, brittle, and light-colored scalp and body hair (hypotrichosis); and absent or decreased or abnormally shaped teeth (hypodontia). HED can be subdivided into types based on how they are inherited and the gene associated with it. Clinically, the subtypes of HED are indistinguishable, given that there is complete overlap between the features of all subtypes. There is an autosomal dominant type (AD), and autosomal recessive type (AR), and an X-linked type. The majority of individuals who have HED have the type inherited in the X-linked manner called X-linked Hypohidrotic Ectodermal Dysplasia or XLHED.
Because XLHED is inherited in an X-linked manner, boys are generally severely affected and female carriers are variably affected.
XLHED is associated with other symptoms, which include dry and scaly skin or eczema, dry eyes, asthma, dry mucous membranes in the mouth, ears, and nose, chronic sinus infections (chronic sinusitis) and a smaller than expected number (reduced) of mucous glands in the throat and lungs.
Individuals with XLHED have life long issues to deal with:
- Skin: dry skin, eczema cause irritation for individuals with HED. In addition, there are a decrease in salivary glands and mucous membranes. This can cause an increase in the number of nose and ear concretion (solid mass) and an increase of sinus infections. To treat these features, individuals with XLHED may require a humidifier or removal of these concretions and medication to assist with sinus infections. Follow up with an ear-nose-throat specialist would be beneficial.
- Sweat glands: Increase in the formation of nose and ear Since the sweat glands are absent or immature, therefore producing little or no sweat, the body does not have this way to cool itself off. Therefore, individuals with XLHED they are at risk for overheating (hyperthermia). Without intervention, this can lead to febrile fevers and death in infancy or toddler years.
- Dental: Most boys only develop 4 to 6 adult teeth, and those that do form, are often misshaped. Therefore, these individuals often wear dentures until they stop growing, at which time they may have dental implants.
SOURCE: Emory University - Department of Human Genetics in collaboration with ThinkGenetic • https://www.thinkgenetic.com/diseases/x-linkedhypohidrotic-ectodermal-dysplasia/overview/17313 • DATE UPDATED: 2016-06-11