Xeroderma pigmentosum (lenticular melanosis, malignant lentigo, pigmented atrophoderma) is a chronic hereditary disease caused by hypersensitivity of the skin to solar radiation and UV rays. Skin changes are characterized by successive processes of inflammation, hyperpigmentation, atrophy, hyperkeratosis and malignant transformation of skin cells. Most patients have eye damage: conjunctivitis, keratitis and tumors. The diagnosis is established upon detection of hypersensitivity of the skin to UV and a characteristic histological picture. Treatment is symptomatic.
General information
According to statistical studies conducted by dermatology, xeroderma pigmentosum occurs on average with a frequency of 1 case per 250 thousand people. The highest incidence is observed among the population of the countries of the Middle East and the Mediterranean coast of Africa. Xeroderma pigmentosum affects both sexes, but some dermatologists note that the disease is more common among girls. The disease is often of a family nature and is observed in closely related marriages.
Causes
There are 2 genotypes of xeroderma pigmentosum: transmitted by autosomal dominant and autosomal recessive. The disease is based on a genetically determined deficiency of the enzymes UV-endonuclease and polymerase-1, which are responsible for the restoration of DNA after its damage by UV rays. In this regard, patients develop skin and eye lesions after being exposed to increased solar radiation. Some heterozygous carriers of the gene have erased forms of pigment xeroderma in the form of various pigment disorders.
Symptoms
Most often (in 75% of cases), the onset of xeroderma pigmentosum occurs in the first 6-12 months of life. The disease manifests itself in spring or summer, as soon as the child comes under intense exposure to sunlight. In some cases, the initial manifestations of xeroderma pigmentosum were observed in patients aged 14-35 years and even at the 65th year of life.
During the xeroderma pigmentosum, 5 stages are distinguished that pass into one another: erythematous, hyperpigmentation stage, atrophic, hyperkeratic and the stage of malignant tumors.
The erythematous stage is characterized by inflammatory skin changes in areas exposed to ultraviolet light. In such areas of the skin, redness, swelling, small bubbles and blisters appear. After the resolution of the elements of the first stage, brown, yellowish or brown pigment spots similar to freckles remain on the skin (the stage of hyperpigmentation).
Subsequent irradiation of the skin in patients with xeroderma pigmentosum leads to new inflammatory and pigmented skin changes, which causes the development of atrophic processes. The disease passes into an atrophic stage, which is characterized by thinning and dryness of the skin, the formation of cracks and scars. The skin is stretched and does not gather into folds. There is a decrease in the mouth (microtomy), atresia of the mouth and nose openings, thinning of the tip of the nose and ears.
The hyperkeratic stage is manifested by the development of warty growths, papillomas, keratomas, fibroids in the foci of the affected skin. The stage of malignant tumors is observed, as a rule, 10-15 years after the onset of xeroderma pigmentosum. But sometimes malignant neoplasms appear in the first years of the disease. Malignant tumors found in v include basal cell carcinoma, melanoma, endotheliomas, sarcomas, trichoepitheliomas, angiosarcomas. They are characterized by rapid metastasis to internal organs, leading to a fatal outcome of the disease.
In 80-85% of cases of xeroderma pigmentosum, eye lesions are observed in the form of conjunctivitis, keratitis, hyperpigmentation and atrophy of the iris and cornea, leading to decreased vision. Telangiectasia, hyperkeratosis, dyschromia and tumor processes appear on the skin of the eyelids. Often, xeroderma pigmentosum is combined with dystrophic tissue changes: dental dystrophy, syndactyly, congenital alopecia, stunting. Xeroderma pigmentosum, accompanied by mental retardation of the child, is isolated as a separate clinical form — de Sanctis-Cacione syndrome.
Diagnostics
A specific method of diagnosing xeroderma pigmentosum is carried out using a monochromator and consists in detecting hypersensitivity of the skin to the effects of ultraviolet light.
To clarify the diagnosis, the dermatologist prescribes a biopsy of the affected area of the skin. Subsequent histological examination at an early stage of the disease determines hyperkeratosis, edema and inflammatory infiltration of the dermis, thinning of the germ layer, pigmentation of the basal layer. In the atrophic and hyperkeratic stages, atrophy of the epidermis, degenerative changes in collagen and elastic fibers are observed. In the stage of malignant tumors — atypical cells and histological picture of skin cancer.
Treatment
Patients should avoid exposure to UV rays: wear hats with large brims and veils, apply sunscreens and ointments, use powders with tannin. Drug treatment of xeroderma pigmentosum is mainly symptomatic and, unfortunately, ineffective. Aromatic retinoids, tocopherol, and hingamine are used. With the development of malignant processes, prospidin, pyridoxine, thiamine, cyanocobalamin are additionally prescribed. Papillomatous and warty growths are surgically removed by cryodestruction, electrocoagulation or laser removal.