Description, Causes and Risk Factors:
Ectodermal dysplasias (EDs) are a heterogeneous group of disorders characterized by developmental dystrophies of ectodermal structures. The X-linked recessive ED is the most common disordere (80% of EDs); it affects males and is inherited through female carriers. It is characterized by the triad of signs comprising sparse hair (atrichosis or hypotrichosis), abnormal or missing teeth (anodontia or hypodontia) and inability to sweat due to lack of sweat glands (anhidrosis or hypohidrosis). The lack of teeth and the special appearance were reported to be major concerns. The incidence in male is estimated at 1 in 100,000 births, the carriers-incidence is probably around 17.3 in 100,000 women.
Most patients with ED have a normal life expectancy and normal intelligence. However, the lack of sweat glands may lead to hyperthermia, followed by brain damage or death in early infancy, if unrecognized. Thus an early diagnosis is important. Families with ED should therefore be offered genetic counseling. Currently the genes and gene products are defined, but the function of the proteins is not fully known. Once the exact function is known, we can understand the embryogenesis and morphogenesis of the ectodermal structures. It is quite possible that these kinds of observations of gene function and interaction may form the basis of new therapeutic methods in the future.
Ectodermal dysplasia results from the abnormal development of embryonic ectodermal structures. The genetic defects responsible for approximately 30 of the ectodermal dysplasias have been identified. X-linked recessive hypohidrotic ectodermal dysplasia is caused by mutations in EDA, which encodes the ectodysplasin protein, a soluble ligand that activates the NF-kappaB and JNK/c-fos/c-jun signaling pathways. Ectodysplasin is important in promoting cell survival, growth, and differentiation.
Autosomal dominant and autosomal recessive hypohidrotic ectodermal dysplasia are caused by mutations in the DL gene, which encodes the EDA (ectodysplasin) receptor. Autosomal recessive hypohidrotic ectodermal dysplasia may also result from mutations in the EDARADD gene, which encodes a protein that interacts with the EDA receptor.
Hidrotic ectodermal dysplasia, which is an autosomal dominant disorder, is caused by mutations in GJB6, which encodes connexin 30, a component of intercellular gap junctions.
EDA-ID and OL-EDA-ID are both caused by mutations in the NEMO gene, which encodes the regulatory subunit of the inhibitor-kappa kinase complex that regulates NF-kappaB activity.
AEC (Hay-Wells) syndrome, Rapp-Hodgkin syndrome, EEC syndrome, limb-mammary syndrome, split hand-split foot malformation syndrome, and acro-dermato-ungual-lacrimal-tooth (ADULT) syndrome are all caused by mutations in the TP63 gene, p63 is a transcription factor that regulates the activity of the tumor suppressor gene TP53.
The frequency of the different ectodermal dysplasias in a given population is highly variable. The prevalence of hypohidrotic ectodermal dysplasia, the most common variant, is estimated to be 1 case per 100,000 births.
There are many types of ectodermal dysplasia (ED), but all of them affect at least two of the ectodermal structures — the skin, hair, nails, teeth, mucous membranes and sweat glands.
Signs of ED may include:
Abnormal or missing teeth.
Inability to sweat because of abnormal or absent sweat glands, which affects the body's ability to regulate temperature.
Sparse, thin hair on the scalp and body.
Abnormal fingernails and toenails.
This X-linked recessive disorder affects males andis inherited through female carriers. The diagnostictool is the typical clinical physiognomy.
The most characteristic findings in man are thereduced number and abnormal shape of teeth. Thedelay in teethening is often the first step in thediagnosis. The men have an easily recognizablefacies, also referred to as an `old man' facies. Someinfants have a premature look with scaling of theskin. This can also form a clue to the diagnosis. Thenumber of sweat glands is reduced and both scalpand body hair are sparse, with lack of eyebrows andeyelashes. The carrier female has some phenotypicexpressions. The clinical findings in carrier femalesare the same as those in affected males. One thirdof the carriers appears healthy, another third ofthem is showing mild symptoms, and the last thirdexhibits significant symptoms, but often milder thanthe affected males.
A genetic evaluation helps determine if the condition is isolated or is part of another syndrome or condition. There are more than 150 medically distinct, inherited syndromes in which ED is present, which affect the skin, sweat glands, hair, nails and teeth in different ways. The most common form of ED is called X-linked ectodermal dysplasia. Boys with X-linked ED usually have several missing teeth and conical-shaped front teeth. Girls with X-linked ED have milder and more variable symptoms, but they may also have missing and abnormally-shaped teeth.
Children with ectodermal dysplasia present many and different clinical problems from early childhood through adolescence and also present a lifelong need for maintenance care and revisions. For the patients as well as the dentists tooth agenesis and its secondary effects on growth and development of the jaws is often the most significant clinical problem. The course of the treatment is to restore the function and the aesthetics of the teeth, normalize the vertical dimension and support the facial soft tissues. As long as there are no physical, psychological or social burdens, no treatment is necessary. Early placement of partial or full dentures is commonly recommended from the age of two or three years onwards. The denture must be periodically modified as alveolar growth erupting teeth and rotational jaw growth change both the alveolar, occlusal and basal dimensions. In children, breakage and even loss of removable prostheses is quite common. They have also a limited retention and stability, a fastened bone destruction of an already hypoplastic alveolar process and the middle of the upper jaw is covered and so it blocks the sutural growth. For this reason, in young children we prefer a treatment with crowns and bridges.
Prior to that it is generally advantageous to modify the crowns of the existing teeth with direct or indirect composite crowns. When conical anterior teeth are crowned the appearance of the child is very much normalized. Restauration of facial height improves both facial aesthetics and speech.
Consultation with the following specialists may be necessary:
Dermatologists can assist in the diagnosis of ectodermal dysplasia and in the management of patients with chronic eczematous dermatitis or scalp erosions.
Plastic surgeons can provide evaluation and management of cleft lip and/or palate defects, other facial defects, and hand and foot defects.
Speech and physical or occupational therapists can assist patients with cleft lip and/or palate with feeding and speech difficulties and can provide therapy to assist patients with hand and foot defects.
Genetic counselors can provide patients and families with assistance in diagnosis and genetic analysis.
Immunologists can help with the evaluation for suspected immunodeficiency.
General dentists or periodontal dentists can provide regular preventative dental care and restorative service as indicated.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
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