Riehl's Melanosis was first described by Riehl, who considered it a photosensitive disease and phototoxic dermatitis. It is characterized by marginal patchy pigmentation on the face, mild telangiectasia, grade I follicular keratosis, and fine scaling.

bubble_chart Etiology

It is believed to be caused by photosensitivity and mechanical stimulation. Cosmetics containing tar derivatives can lead to photosensitivity, and malnutrition may also contribute to the condition.

bubble_chart Pathological Changes

Hyperkeratosis and follicular keratin plugs, grade I atrophy of the spinous cell layer, liquefaction degeneration of the basal cell layer, dilation of superficial dermal capillaries, and increased melanophages. Perivascular cellular infiltration, predominantly lymphocytes.

bubble_chart Clinical Manifestations

The disease begins with grade I cutaneous pruritus and erythema, followed by pigmentation. The pigmented patches have indistinct borders, with the color gradually deepening and spreading, appearing as light brown, grayish-brown, brown, or dark brown. The pigmented areas exhibit grade I congestion and capillary dilation. The surface of the skin lesions has diffuse, fine, thin scales, resembling a dusting of flour, and may show grade I atrophy and follicular hyperkeratosis. The mucous membranes remain unaffected. The primary affected areas are the forehead, cheekbones, preauricular and postauricular regions, and both sides of the neck, with the central face rarely involved. Sometimes, it also occurs in friction-prone areas such as the armpits, navel, forearms, and chest. The dorsal surfaces of the fingers and the scalp near the hairline show lighter pigmentation. The condition follows a chronic course, with lesions stabilizing after reaching a certain stage. Over time, the pigmented patches gradually lighten, hyperkeratosis diminishes, and spontaneous recovery occurs. According to Tadokor's report, the incidence ratio of females to males is 77:8. Sixty percent of patients exhibit photosensitivity. Clinical observations reveal that while female patients are more common, male patients are also frequently seen. The disease generally presents no systemic symptoms and does not involve mucous membrane damage.

Avoid taking photosensitive drugs and using cosmetics containing tar derivatives, and reduce mechanical irritation to the skin.

The application of vitamins, such as vitamins A, B, and C, is particularly important, with vitamin C being the most crucial. Take 1-3g daily or administer 2g of vitamin C intravenously each day. Vitamin E can also be taken orally or applied topically as a 1% vitamin E cream to improve skin nutrition.

For topical use of depigmenting agents, a 3-5% hydroquinone cream is more effective, but care must be taken to avoid uneven fading due to excessive application.

bubble_chart Differentiation

(1) Differentiation from Civatte's poikiloderma: Civatte's poikiloderma occurs on the cheeks, neck, and anterior chest, presenting with reticulated pigmentation, pale spotted skin atrophy, and prominent telangiectasia. In contrast, this condition manifests as marginal pigmentation on the forehead, zygomatic area, preauricular and retroauricular regions, and neck, accompanied by grade I keratosis and fine scaling, resembling a dusting of powder on the face.

(2) Melanodermatitis toxica lichenoides is caused by prolonged exposure to asphalt, coal tar, petroleum, or inhalation of their volatile substances. It features pruritic reticulated pigmented patches on the face, chin, and neck, along with telangiectasia, black lichenoid follicular papules, and acne-like inflammatory reactions, making it easily distinguishable from this disease.