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New Treatments for  Darier Disease (Keratosis Follicularis)

This rare genetic disorder is inherited as an autosomal dominant trait. Onset occurs usually during late childhood. Typical lesions are small, firm, skin-colored papules that are not always follicular in location. The lesions eventually acquire yellow, malodorous crusts; coalesce to form large, gray-brown, vegetative plaques; and usually involve the face, neck, shoulders, chest, back, and limb flexures in a symmetric distribution. Papules, fissures, crusts, and ulcers may appear on the mucous membranes of the lips, tongue, buccal mucosa, pharynx, larynx.

Hyperkeratosis of the palms and soles and nail dystrophy with subungual hyperkeratosis are variable features. Severe pruritus, secondary infection, offensive odor, and aggravation of the dermatosis on exposure to sunlight may occur. Darier disease is most likely to be confused with seborrheic dermatitis or juvenile flat warts.

Hyperkeratosis, intraepidermal separation with formation of suprabasal clefts, and dyskeratotic epidermal cells are characteristic features.

Treatment is nonspecific. Some patients have responded to topical vitamin A or retinoic acid, with or without occlusive dressings. Severe disease may be controlled with oral synthetic retinoids. Secondary infection may require local cleansing and systemically administered antibiotics.

Lichen nitidus is a chronic, benign, papular eruption is characterized by minute (1-2 mm), flat-topped, shiny, firm papules of uniform size; these are most often skin colored but may be pink or red. In black individuals, they are usually hypopigmented. Sites of predilection are the genitals, abdomen, chest, forearms, wrists, and inner aspects of the thighs. The lesions may be sparse or numerous and form large plaques; careful examination usually discloses linear papules in a line of scratch (Koebner phenomenon), a valuable clue to the diagnosis because it occurs in only a few.

Lichen nitidus occurs in all age groups. The cause is unknown. Patients are usually asymptomatic and constitutionally well. The lesions may be confused with those of lichen planus and rarely coexist.

Widespread keratosis pilaris can also be confused with lichen nitidus, but the follicular localization of the papules and the absence of Koebner phenomenon in the former distinguish them. Verruca plana (flat warts), if small and uniform in size, may occasionally resemble lichen nitidus. Although the diagnosis can be made clinically, a biopsy is occasionally indicated. Histopathologically, the lichen nitidus papule consists of sharply circumscribed nests of lymphocytes and histiocytes in the upper dermis enclosed by clawlike epidermal rete ridges. The course of lichen nitidus spans months to years, but the lesions eventually involute completely. There is no

Pityriasis rubra pilaris is a rare chronic dermatosis often has an insidious onset with diffuse scaling and erythema of the scalp, which is indistinguishable from seborrheic dermatitis, and with thick hyperkeratosis of the palms and soles. The characteristic primary lesion is a firm, dome-shaped, tiny, acuminate papule, which is pink to red and has a central keratotic plug pierced by a vellus hair. Masses of these papules coalesce to form large, erythematous, sharply demarcated orangish plaques, within which islands of normal skin can be distinguished, creating a bizarre effect. Typical papules on

Etiology.

The cause is unknown. A genetic form with autosomal dominant transmission may account for some cases in childhood, but most appear to be sporadic. Attempts to link the disease with a defect in vitamin A metabolism have not been definitive. Skin biopsy may help to differentiate this condition from psoriasis

Treatment.

The numerous therapeutic regimens recommended are difficult to evaluate because the disease has a capricious course with exacerbations and remissions. Oral and topical retinoids and