During conception, cells are formed into three cell layers: endoderm, mesoderm, and ectoderm. The ectoderm, which is the outer layer, differentiates into skin, nails, hair, sweating glands, teeth, eyes, inner parts of the ear, brain, spinal cord, nerves, retina of the eye, and pigment cells of the human body. Ectodermal Dysplasia (ED) is a hereditary disease with various clinical manifestations that involve two or more of the ectoderm tissues, such as skin, hair, nails, eccrine glands, and teeth, which appear as defects of ectoderm formation. Ectodermal dysplasia has been found in more than 150 syndromes, some of which show similar symptoms even with different genes involved. The ectoderm dysplasia affects to varying degrees all the structures involved in the development of skin tissue. The skin is weak and is accompanied by alopecia, nail dysplasia, local keratin dermatosis. Various types of ectoderm dysplasia have been described, with the most common being hypodermic ectoderm (Hypohidrotic ED) and percutaneous ectoderm dysplasia (Hidrotic ED), which are inherited as X-linked recessive. The incidence is reported to be greater than seven out of about 10,000.
Various forms of Ectodermal Dysplasia are known according to the characteristics of clinical features.
Anhidrotic, Hypohidrotic ectoderm (Christ-Siemens-Touraine syndrome): inherited primarily as X-linked recessive, and sometimes autosomal recessive. There is no sweat gland and sweating is poor due to the hypoplasia of the eczema. In affected patients, high temperatures may occur due to inability to sweat in hot conditions and poor body temperature control. The reduction of hair follicles leads to hypopotosis, which causes the hair to be sparsely colored, pale in color, sinuous, and lacking or sparse eyebrows. Lacking sebaceous glands, the skin is dry and wrinkled, and the skin is pale with pigment hypoplasia. In newborns, skin flaking is often a clue to diagnosis. Respiratory infections, rhinitis often occur due to hypoplasia of salivary and lacrimal glands and mucous glands of respiratory and digestive organs, accompanied by dysphonia, dysphagia, and diarrhea. About 30% of patients may die before age 2 due to high fever or respiratory infections. The shape of the face is characterized by protrusions of the frontal head, hypoplasia of the cheekbones, flat noses, abducted lips, wrinkled and hyperpigmented skin around the eyes, and low-ear ears. There is a wide gap between the teeth due to abnormalities of teeth, non-forming or low-shaping of teeth. Rarely, stenosis of the tear glands, corneal clouding, cataracts, hypoplasia or no formation of the mammary gland, and conductive hearing loss are also observed. The frequency of atopic dermatitis is high. Female carriers have varying degrees of symptoms such as abnormal teeth, thinning hair, and sweating.
Hirotic ectoderm dysplasia (Clouston syndrome): characterized by hypoplasia or dysplasia of the nails, sparse hair, hyperkeratosis of the palms and soles of the feet. Conjunctivitis and eyelid infections are common and do not have eyebrows or eyelashes. Small tooth size and frequent tooth decay, but teeth are normal. The skin of the knees and elbows is over pigmented.
EEC (Ectodermal dysplasia, Ectrodactyly, Clefting) syndrome: inherited as an autosomal dominant, variable in expression and low in penetrancce. EEC syndrome can have a variety of clinical manifestations: ophthalmic toenails (ectrodactyly), nail hypoplasia, cleft lip, cleft palate, lacrimal gland abnormalities, dry and white skin, loose hair and eyebrows, teeth abnormalities, hearing loss, strabismus It is characterized by abnormalities in the urinary tract and the like. Skin biopsy shows a reduced number of hair follicles and sebaceous glands.
AEC (Ankyloblepharon, Ectodermal dysplasia, Cleft / lip / palate) syndrome (Hay-Wells syndrome): It is inherited as an autosomal dominant and shows various expressions. Skin torsion and redness are present at birth and include ankyloblepharon, wide snorting, maxillary hypoplasia and cleft palate. Inflammatory dermatitis of the scalp develops alopecia, accompanied by eyelid and conjunctivitis. Missing nails or dysplasia and decreased sweating.
Rapp-Hodgkin syndrome: inherited as autosomal dominant. Forehead, narrow nose, accompanied by cleft lip, cleft palate, tooth hypoplasia, sinuous and coarse hair, alopecia due to dermatitis of the scalp, and nail hypoplasia. Rarely, deafness and urethral fever appear.
Ectodermal dysplasia is caused by mutations in several different genes in each clinical form. The most common type, X-linked hypohidrotic ectodermal dysplasia, is an X-linked recessive gene, more than 90% of which is expressed in boys. The gene is located on the X chromosome armband q11-21.1 and is caused by a mutation in ectodysplasin, a byproduct of the EDA (ectodysplasin-A) gene. In addition, hypodermic ectoderm dysplasia is rarely related to the autosomal dominant or recessive EDAR and EDARADD genes and the autosomal recessive WNT10A gene. Percutaneous ectoderm (Clouston’s hidrotic ectodermal dysplasia) is inherited as an autosomal dominant gene and is caused by mutations in the GJB6 gene encoded to produce connexin 30, a component of intercellular gap junctions. AEC syndrome, Rapp-Hodgkin syndrome and EEC syndrome are caused by mutations in the TP63 gene. Autosomal recessive genetic ectoderm dysplasia is also involved in the mutation of the EDARADD gene. In this case, both men and women can be patients. (delete)
Since ectoderm dysplasia is inherited in a variety of ways, there are different disease risks for each genetic pattern. In case of inherited autosomal recessive, mother and father become carriers of mutation, and if they have a baby brother, there is a 1/4 chance that they will be ill. The same carrier. On the other hand, if inherited as an autosomal dominant, there are two cases. If one of the parents is a patient with the same mutation, the child’s brother has a 1/2 chance of getting the disease. On the other hand, if both parents are normal, it is a de novo mutation by chance when the child is born, and in this case, the probability of disease is very low when the next brother of the patient is born. In the case of X-linked genetics, the male mother is the carrier, and the female sisters have a 1/2 chance of inheriting the mother’s mutation.
Diagnosis is based on the characteristic clinical symptoms. Two or more of the five symptoms represented by hair dysplasia, tooth dysfunction, nail dysplasia, sweating disorder, and skin disorder can be diagnosed as ectoderm dysplasia. This can be confirmed by genetic mutation testing, and prenatal diagnosis by genetic testing is also possible in families where mutations are found. Examining the skin of the palm of your hand can help to diagnose the hypoplasia of the epidermal gland.
There is no specific treatment, but it can be helped in a supplementary way depending on your symptoms. Patients with involuntary ectoderm dysplasia are either unable or unable to sweat due to deficiency of the sweat gland, and thus cannot control body temperature due to sweating, which causes severe high fever and difficult to control body temperature. In particular, the younger it is severe, and even adult patients can not withstand the hot environment, so special care is needed to maintain normal body temperature. Avoid exposure to high temperatures, and in hot weather, use a thin cloth or air conditioner to control your temperature. Early denture care and the use of dentures can be both cosmetic and nutritional. Ophthalmology uses artificial tears to prevent corneal damage. In the case of the respiratory tract, an infection is actively treated with bronchodilators or antibiotics. In the case of severe alopecia, a wig is worn.
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