What is Hypohidrotic Ectodermal Dysplasia?

Hypohidrotic ectodermal dysplasia, or anhidrotic ectodermal dysplasia, refers to a group of rare congenital disorders typically causing abnormal prenatal development of hair, skin, sweat glands and teeth. Body organs and skeletal tissue might also be affected. The anomaly primarily affects male infants, but females may also inherit the disorder. Researchers generally classify the syndromes as autosomal dominant, autosomal recessive, or X-linked. Christ-Siemens-Touraine syndrome, Hermann Werner Siemens and Rapp-Hodgkin syndrome belong to this large assembly of conditions.

Symptoms vary depending on whether the disorder is sex-linked or autosomal; the sex-linked variety typically presents more severe traits. In addition to obvious physical deformities, the common trait of missing or malfunctioning skin glands results in the body’s inability to hydrate the skin or form perspiration. These children are easily subject to hyperthermia and must use external cooling methods to prevent multi-organ damage.

Children born with the form of hypohidrotic ectodermal dysplasia known as Christ-Siemens-Touraine syndrome generally have brittle, fine, short blond hair that is usually sparse in nature. Their dry, shiny smooth skin is grayish-white in color and frequently lacks or contains malfunctioning oil and sweat glands. When these infants begin growing teeth, they are also sparse and malformed in appearance. The syndrome usually produces distinct facial features, which includes deformed ears, a flat saddle-bridged nose, a protruding forehead and thickened lips. Boys especially may be small in stature and appear feminine.

The hypohidrotic ectodermal dysplasia disorder known as Hermann Werner Siemens primarily causes cutaneous conditions. Youngsters develop keratosis pilaris, or bumps and rashes around hair follicles, that cause the openings to close and give the skin an overall goose-bump likeness. The trauma the hair shaft endures while forcing its way to the surface frequently results in damage and an altered appearance, as each hair becomes somewhat tufted. Groups of these tufted hairs produce a woolly patch. The disorder initially affects the hair on the face and scalp, including the eyebrows and eyelashes, but eventually affects the entire surface of the body.

The skin eczema that results is generally itchy and prone to infections, which are typically treated with topical steroids and oral antibiotics. The scarring caused by the cycle of skin rashes may eventually produce baldness. These children might also experience thickened eyelids, have corneal or lower jaw deformities, and be very sensitive to the sun.

Rapp Hodgkin is a genodermatoses with characteristics resembling many other hypohidrotic ectodermal dysplasia disorders, in that children typically have the sparse hair and either lack or have malfunctioning skin glands. Additionally, these infants may be born with cleft palates affecting the roof of the mouth and the upper lip. Finger and toenails also grow abnormally, and the youngsters overall typically experience retarded physical growth.