Atrophic form of red squamous lichen planus as a cause of alopecia areata

This rare clinical form of lichen planus accounts, according to various authors, for 2% to 10% of all forms of dermatosis. It manifests itself as flat, slightly elevated papules of a pale pinkish-bluish color up to the size of a lentil, which sometimes form annular foci. In places of initially papular rashes, characteristic of lichen planus, small, clearly defined atrophic areas of skin are formed, somewhat sunken in relation to the surrounding skin and devoid of hair and openings of hair follicles. Usually, not all papules of lichen planus undergo such a transformation; some of the rashes typical of this dermatosis remain on the skin, the visible mucous membrane of the mouth and on the genitals. In some cases, there is also characteristic dystrophy of the nails. Atrophic lesions on the skin are the final stage of the evolution of lichen planus papules, i.e. occur secondarily, which greatly facilitates the clinical diagnosis of this form of dermatosis. The rash is most often located on the skin of the trunk, genitals, limbs, and also the scalp, where the pseudopelade condition is formed. The rash elements often appear in small quantities, but can group and merge into larger, clearly delineated areas of skin atrophy with pigmentation, less often - depigmentation. Atrophic changes in the skin often occur within annular foci, which can be the only manifestation of the dermatosis or combined with the rashes described above. Annular lesions usually have a small diameter (about 1 cm) and can gradually increase in size, reaching 2-3 cm. Their central part is sharply defined, smooth, atrophic, unevenly pigmented; the peripheral part is represented by an elevated, continuous brownish-bluish rim surrounding an atrophic brownish center. Many authors note the long, persistent course of annular atrophic lichen planus.

Histopathology

The epidermis is atrophic, thinned, epithelial outgrowths are smoothed, hyperkeratosis and hypergranulosis are expressed less strongly than in the typical form. The dermal papillae are absent, the strip-like infiltrate in the dermis characteristic of the usual form is rare, more often it is perivascular, sometimes rather scanty, consisting mainly of lymphocytes; in the subepidermal areas, proliferation of histiocytes is noted. It is always possible, although with difficulty, to find separate areas of the lower border of the basal layer "blurred" by the infiltrate cells; elastic fibers are almost completely absent in the infiltrate area.

Diagnostics

On the scalp, foci of atrophic lichen planus are differentiated from other dermatoses that lead to pseudopelade. Secondarily occurring small areas of atrophy the size of a lentil on the skin of the trunk and extremities are clinically very similar to the manifestations of small-focal scleroderma, or scleroatrophic lichen. With rare localization on the scalp, it can also lead to pseudopelade. In cases where, in addition to pseudopelade and small foci of atrophy on other areas of the skin or mucous membrane, typical manifestations of lichen planus are found, diagnosis is facilitated. The results of the histological examination of the affected skin are decisive, as they differ significantly in these dermatoses.

Annular lesions of atrophic lichen planus may resemble cicatricial basalioma, Bowen's disease, sometimes discoid lupus erythematosus, annular granuloma, when localized in the occipital region, back and lateral surfaces of the neck - elastosis perforans serpiginosa, and on the genitals - orbicular syphilid.

It is also necessary to take into account the rare possibility of developing basal cell epithelioma of the skin on the scalp, resembling focal scleroderma (sclerodermaform basalioma). Metastases to the scalp are also quite rare. They develop in people who have previously undergone surgical treatment for breast cancer or other localizations, and can manifest as sclerosing foci of alopecia. If a neoplastic process is suspected, a histological examination of the skin should be performed.

[ 1 ], [ 2 ], [ 3 ], [ 4 ]