Ectodermal Dysplasia (ED) is not a single disorder, but a group of closely related conditions of which more than one hundred and sixty different syndromes have been identified. The Ectodermal Dysplasias (EDs) are genetic disorders affecting the development or function of the teeth, hair, nails and sweat glands. Depending on the particular syndrome ED can also affect the skin, the lens or retina of the eye, parts of the inner ear, the development of fingers and toes, the nerves and other parts of the body. The prevalence of the various types of ED is thought to be about 7 in 10,000 live births. EDs have been reported most often in caucasians, but they occur in all population groups. Hidrotic ED has been reported in an extensive kindred of French extraction. X-linked hypohidrotic ED has full expression predominantly in males. Female carriers outnumber affected men, but most show few, if any, signs of the condition although some do manifest it very clearly. Most of the other EDs affect males and females equally.

Each syndrome usually involves a different combination of symptoms, which can range from mild to severe, such as:

• Absence or abnormality of hair growth;
• Absence or malformation of some or all teeth;
• Inability to perspire, which causes overheating;
• Abnormalities of the nails - which may be brittle and grow slowly or be thickened or ridged;
• Frequent infections due to immune system deficiencies or, in some cases, the inability of cracked or eroded skin to keep out disease-causing bacteria;
• Absence or malformation of some fingers or toes;
• Cleft lip and/or palate;
• Irregular skin pigmentation.

In addition to the above they may have:

• Sensitivity to light;
• Respiratory infections and allergies;
• A lack of breast development;
• Impairment or loss of hearing or vision;
• Constipation;
• A host of other challenges.

Individuals affected by ED face a lifetime of special needs which may include:

• Dentures at a young age with frequent adjustments and replacements;
• Special diets to meet dental/nutritional needs;
• Air conditioned environments;
• Wigs to conceal hair and scalp conditions;
• Genetic testing to confirm the precise diagnosis and identify carriers;
• Protective devices from direct sunlight;
• Osseointegrated dental implants;
• Respiratory therapies.

In some cases, an ED is apparent at birth. In other cases, it may become evident when teeth fail to develop normally. Different types of ED are diagnosed according to the grouping of features. Complex forms of ED may affect the development or function of other body structures, as well.

It is important to remember that not all individuals affected by the EDs will have physical features that fit the description of a specific syndrome. There may be a great deal of variation in the physical appearance of the same type of ED from one affected person to the next. It is also conceivable for a person to have a type of ED that has not yet been described. Nonetheless, the EDs share certain features, an understanding of which makes it possible to appreciate the ramifications for most affected individuals and allows everyone involved to respond appropriately to the individual's needs.

Eye Problems and Ectodermal Dysplasia

The ectodermal dysplasias cause four main ocular problems:

• Tears Deficiency. Tears are composed of a mucus layer, water or aqueous layer and an oil layer, and ED can affect any of these layers. Defects in the tear film can predispose to infection, lead to corneal ulceration and delay healing. Treatment for tear deficiency includes tear replacement eye drops and punctal plugs (plugs that prevent tears being lost from the eyes through drainage through the nose) or occlusion (blockage) that reduce the loss.
• Tear drainage. The tear drainage system drains tears from the eye into the nose. Obstruction in this system can cause watery eyes especially from birth and dacryocystitis (infection of the tear drainage sac). Surgery may be required for blockage of the nasolacrimal duct (tear/drainage path) and this includes syringing and probing the system (usually done in childhood) and dacryocystorhinostomy or DCR (operation to 're-plumb' the duct into the nose).
• Cornea. The health of the cornea is essential for vision and corneal ulceration and scarring can result from dry eyes, recurrent infections, stem cell failure and misdirection of the eyelashes. Corneal problems are commonly seen in ectrodactyly-ectodermal dysplasia and ectrodactyly, ectodermal dysplasia and cleft lip/palate syndrome (EEC syndrome). Corneal ulcers are treated by a variety of measures - antibiotics, tear supplements, patching and special contact lens termed bandage contact lenses. Corneal transplantation and ocular surface reconstruction may be concerned in some cases of corneal scarring to restore vision.
• Lens. The lens forms from the ectoderm (surface skin). A cataract (cloudiness of the lens) results in defects in focus and clarity of vision. These cataracts can be congenital (present at birth) and, if dense, result in poor vision from birth, wobbly eyes or nystagmus and loss of the red reflex. Congenital cataract surgery is a complex procedure requiring careful visual rehabilitation.

Inheritance patterns
These are variable according to the specific type of ED. Patterns include autosomal dominant, autosomal recessive, X-linked dominant, X-linked recessive. For hypohidrotic ED, inheritance is usually X-linked but can be autosomal dominant or autosomal recessive. Cases can arise as isolated (sporadic) cases within a family, when the mode of inheritance may be unclear.

Genetic counselling is available for families.

Prenatal diagnosis This is available for some families with X-linked hypohidrotic ectodermal dysplasia using molecular genetic methods including mutational testing or linkage analysis but is not possible for all families.

A gene has been identified on chromosome 2 which is involved in some cases of autosomal hypohidrotic ED, and testing for this has recently become available as a regular diagnostic service.

Medical text written October 2005 by the Ectodermal Dysplasia Society and Contact a Family. Approved October 2005 by Professor A Clarke, Professor in Clinical Genetics,Institute of Medical Genetics, University of Wales College of Medicine, Cardiff, UK. Additional material on Eye Problems and Ectodermal Dysplasia written July 2006 by Dr C Willoughby, Consultant Ophthalmic Surgeon and Senior Lecturer in Ophthalmology, Royal Victoria Hospital, Belfast, UK.

ECTODERMAL DYSPLASIA SOCIETY

Ectodermal Dysplasia Society
108 Charlton Lane
Cheltenham
GL53 9EA
Tel: 01242 261332
e-mail: diana@ectodermaldysplasia.org
Web: http://www.ectodermaldysplasia.org

The Society is a National Registered Charity No. 1089135, established in 1996. It provides information, advice and support to those affected by an ectodermal dysplasia, promotes the education of the medical profession and general public, supports research, encourages a network for mutual support and produces a newsletter. The society has a medical advisory board.

Group details last confirmed April 2007.