Ectodermal dysplasias: causes, symptoms, diagnosis, treatment

Ectodermal dysplasia is a group of hereditary diseases caused by abnormal development of the ectoderm, and combined with various changes in the epidermis and skin appendages.

The causes and pathogenesis of ectodermal dysplasia have not been fully established. Currently, several dozen dermatoses of ectodermal origin have been described in the literature. It is generally accepted that the following two forms are classical: anhidrotic and hydrotic. The anhidrotic form is often inherited in an X-linked recessive manner, less often in an autosomal recessive manner. Familial cases of the disease have been described. The hydrotic form of ectodermal dysplasia is inherited in an autosomal dominant manner. Some scientists believe that under the influence of X-rays, viral infections, and chemical compounds, a violation of disulfide bonds in the L-keratin matrix fraction may occur.

Symptoms of ectodermal dysplasia. Both forms of ectodermal dysplasia develop shortly after birth or in early childhood, with the full clinical picture forming by puberty.

Anhidrotic ectodermal dysplasia (Christ-Siemens syndrome) is a heterogeneous disease, in most cases inherited recessively, linked to the X chromosome, gene localization - Xql2-ql3. The full clinical picture, including such basic signs as anhidrosis, hypotrichosis and hypodontia, is observed, with rare exceptions, only in men.

The anhidrotic form of ectodermal dysplasia occurs predominantly in males. The characteristic signs are the following triad: hypo- or anhidrosis, hypotrichosis, hypodontia. At first, patients experience impaired thermoregulation due to hypo- or aplasia of the sweat glands. Patients with the anhidrotic form suffer from hyperthermia, which can have serious consequences if cases are not recognized. There is a decrease or absence of sweating over the entire skin, with the exception of the localization of apocrine glands, where it may be preserved to a greater or lesser extent. Upon examination, pronounced dryness and thinning of the skin are noted. Some patients have ichthyosiform peeling, follicular hyperkeratosis, barely noticeable keratoderma of the palms and soles. Conjunctivitis, laryngitis, pharyngitis, rhinitis, and stomatitis develop due to dryness. Eyelashes and eyebrows are sparse, there is no hair in the pubic area and armpits. Vellus hair is usually not affected. The appearance of patients is characteristic: tired, senile expression, short stature, large square skull with prominent frontal tubercles, massive chin, brow ridges, high and wide cheekbones, sunken cheeks, bulging lips, large protruding ears (satyr ears), saddle nose, thinning hair up to alopecia. Teeth erupt late, remain in the milk stage for a long time, there is a large distance between the upper incisors, may be incomplete or even completely absent, often deformed. Mental development in most patients is normal, sometimes signs of decreased intelligence, hearing loss, susceptibility to infections are revealed. In women, the disease occurs in a mild form in the form of mild dental anomalies, focal sweating disorders, poor development of the mammary glands.

Hydrotic ectodermal dysplasia (Clouston syndrome) is inherited in an autosomal dominant manner and is characterized by two main symptoms: hypotrichosis and nail abnormalities. The biochemical defect is thought to be a decrease in the number of disulfide bonds in the a-keratin matrix fraction.

In ectodermal hidrotic dysplasia, the main signs are dystrophy of the nails and hypotrichosis, to a lesser extent - palmoplantar keratosis, pigmentation disorder. Sweating is usually not impaired. Changes in the nails are the main, most frequent, and sometimes the only sign of the disease. The nail plates grow slowly, are thickened, brittle, easily break off, brown in color, deformed, and atrophied in places. The edges of the nails are as if eaten away, split, longitudinally striated. Onycholysis may occur.

The hair is thin, dry, breaks easily, thinned, sometimes to the point of total alopecia. Twisted hair, knotty hair fragility, splitting, loss of eyebrows and eyelashes, sparse hair growth in the armpits and pubis may be observed. There are foci of hypo- and depigmentation, sometimes resembling vitiliginous spots. Thickening of the terminal phalanges is detected, changes in the teeth are usually absent or insignificant. With age, the phenomenon of xratoderma intensifies.

Histopathology. In the anhidrotic form of dysplasia, there is an absence of sweat glands, normal structure of hair follicles and sebaceous glands. In hidrotic dysplasia, hypoplasia of hair and sebaceous glands is observed.

Pathomorphology. Histological examination reveals thinning of the epidermis, hyperkeratosis with formation of horny plugs in the mouths of hair follicles, hypoplasia of hair follicles and sebaceous glands. In the anhidrotic form, sweat glands are absent, in the hydrotic form - within normal limits. However, signs of sweating that appear during treatment with tigazone of patients with anhidrotic ectodermal dysplasia indicate that the number of sweat glands is only reduced and / or they are functionally defective (own observations). Changes in hair in both types of ectodermal dysplasia are similar. They are twisted, changed according to the type of nodular trichorrhexis. Often, hair shafts are smaller than normal in diameter, asymmetry of hair follicles, proliferation of cells of their outer root sheath are noted. Among the proliferating cells, there are dyskeratotic; New formation of hair follicles from cells of the outer root sheath is noted. The inner root sheath is thickened and deformed. Scanning electron microscopy revealed a decrease in the diameter of the hair shaft, a change in its shape from round to compacted; cuticle scales are atrophic or absent. Exfoliation of cuticle cells is more noticeable towards the top of the hair. The medulla of the hair has a coarse fibrous structure. Keratinization anomalies are possibly caused by a genetic change in the amino acid sequence in the proteins of the cortex and medulla of the hair, which leads to a disruption in the oxidation of thiol groups between the polypeptides of the filaments of the cortex of the hair.

Differential diagnosis must be carried out with progeria, congenital syphilis, congenital pachyonychia.

Treatment of ectodermal dysplasia is symptomatic. It is necessary to protect patients with the anhidrotic form from overheating.

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