About focal dermal hypoplasia

What is focal dermal hypoplasia?

Focal dermal hypoplasia (FDH), also known as Goltz syndrome, is a rare skin disorder that can also affect bone and eye development. If is a type of ectodermal dysplasia, a group of heritable disorders causing the hair, teeth, nails, and glands to develop and function abnormally. Most cases (about 90 percent) are seen in females. This disorder is characterized by skin abnormalities that develop into streaks or lines of tumor-like lumps on various parts of the body. This syndrome displays a wide array of symptoms and may affect almost any organ. In 2007, scientists at Baylor College of Medicine identified the gene that accounts for most cases of this disorder.



What are the symptoms for focal dermal hypoplasia?

FDH is a rare disorder that primarily affects females and has extreme variability. It is characterized by skin Lesions that look streaked, underdeveloped or “punched-out”, birth defects of the hands and feet and birth defects of the eyes. There may be inflammation, itching, reddening, blistering, and crusting of the skin. Skin may be absent, discolored or lack color (pigmentation) in some areas. The nails may be absent or appear abnormal. Enlargement of capillaries/veins under the skin (telangectasias) often develop with age. Wart-like growth (papillomas) are usually not present at birth but develop with age and are typically found on the gums, tongue, lips, nose, genetalia, and anus. Overgrowth of tissue may be found on the palms of the hands and soles of the feet. Excessive Sweating (hyperhidrosis) or absence of Sweating (hypohydrosis) is often present on the palms of the hands and soles of the feet. Nearly all individuals with focal dermal hypoplasia display at least a few of the skin abnormalities. The hair may be sparse, brittle, and/or missing.

Eye abnormalities are common and are present at birth and can include: drooping eyelids (ptosis); clouding of the cornea; a cleft or keyhole-shaped defect in the iris or the retina (colobmas); small or missing eye (microphthalmia/anophthalmia); wide spacing between the eyes (hypertelorism); crossed eyes (strabismus); and/or exposure of the lining of the eyelid (ectropion).

Individuals with FDH may also have a variety of skeletal abnormalities, some of which may be present at birth. Curvature of the spine (scoliosis), fused vertebrae, underdeveloped or missing fingers or toes, Extra fingers or toes (polydactyly), fingers or toes that have grown together (syndactyly), fingers that bend to the side (clinodactyly), permanently bent fingers (camptodactyly), and/or fusion of bones of the fingers and toes may be present. Other malformations of the skeleton may include a small skull, an underdeveloped jaw, a forward projection of the jaw, and/or uneven development of the face, limbs, or trunk. Cleft lip and palate may be present and may cause feeding, breathing, and vision problems.

Problems within the mouth are seen in more than 50 percent of patients affected. Failure of the teeth to develop properly often occurs in these patients. The teeth may be missing or underdeveloped and are unusually small or improperly spaced. Missing enamel may aid in the development of cavities.

Abnormalities of the ears, the eyes, the heart, central nervous system, gastrointestinal system, and the kidneys may also be present. Abnormalities within the gastrointestinal system may lead to problems with breathing and feeding. Intellectual disability can be found in some instances. Most patients with FDH are noted to be small at birth and have mild short stature.

An extremely wide range of symptoms characterizes FDH, making it difficult to diagnose.



What are the causes for focal dermal hypoplasia?

In June 2007, research funded in part by the National Institutes of Health led to the identification of the gene that accounts for all affected individuals of FDH. The gene is known as PORCN, and it creates proteins important in the development of the skin, skeleton, and eyes in a developing embryo and fetus. Recent studies of patients displaying symptoms consistent with FDH have found genetic changes in the PORCN gene in nearly all affected females.

The PORCN gene is found on the X chromosome and the syndrome is inherited in a X-linked dominant pattern. X-linked dominant disorders are caused by an abnormal gene on the X chromosome and occur mostly in females. Females with these rare conditions are affected when they have an X chromosome with the gene for a particular disease. Males with an abnormal gene for an X-linked dominant disorder are more severely affected than females and often do not survive. Living males with FDH are “mosaic” for a change in the PORCN gene. This means that the change is seen in some, but not all, of the cells in their body.



What are the treatments for focal dermal hypoplasia?

Treatment for patients with focal dermal hypoplasia is directed at the symptoms. Dermatological creams and protective dressings may relieve skin discomfort and prevent secondary infections. Dentures and hearing aids may be required. Heat and over-exercise should be avoided. Limb deformities may be treated with occupational therapy, assistive devices, or surgery. Surgical or laser therapy may be recommended for patients demonstrating trouble swallowing due to large fat deposits in the throat.



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