Melanosis is a gray-brown pigmentation disorder that primarily occurs on the face, most commonly seen in middle-aged women.

This condition should be differentiated from Addison's disease. Addison's disease presents as a uniform darkening of the skin, particularly at the mucocutaneous junctions, and often involves mucous membranes such as the gums. Patients also exhibit symptoms of adrenal cortical insufficiency.

bubble_chart Etiology

Disease cause:
The exact cause is not yet fully determined. Prolonged exposure to tar, asphalt, petroleum, and their derivatives—due to the significant photosensitizing effects of compounds such as anthracene, phenanthrene, and naphthalene—can lead to inflammation in sun-exposed areas, resulting in skin pigmentation changes. Melanosis clearly caused by tar compounds is also known as tar melanosis. Some cosmetics contain mineral oils, hydrocarbons, fragrances, preservatives, surfactants, etc., some of which have photosensitizing properties. Long-term exposure to these substances can lead to melanosis. In some patients, no clear causative factor can be identified.

Pathological description:
The lesion site shows liquefaction degeneration of basal cells, with lymphocyte and histocyte infiltration around the superficial dermal blood vessels. Melanophages and free melanin granules are present around the dermal papillae and superficial blood vessels.

bubble_chart Clinical Manifestations

The skin lesions initially present with mild redness and slight itching, which worsen after sun exposure. Due to the relatively mild symptoms, they often go unnoticed by patients. The condition progresses slowly, and after several months, reddish-brown patches gradually appear on sun-exposed areas such as the face and neck. These patches are diffusely distributed with indistinct borders from the surrounding normal skin. Over time, they evolve into grayish-brown or grayish-purple patches, with punctate pigmentation around the pores, giving the lesions a reticular appearance. Occasionally, grade I reticular telangiectasia, follicular keratosis, and bran-like scales may accompany the condition, though subjective symptoms remain minimal. The lesions predominantly affect the face, particularly the forehead and temples, and may extend to the back of the ears, neck, upper arms, forearms, and other exposed areas. In cases caused by tar, lesions may also appear on the chest and upper back. The disease follows a chronic course.

First, carefully search for the {|###|}disease cause{|###|} and avoid contact with tar-like compounds. Workers exposed to asphalt or tar should pay attention to labor protection and avoid working under strong sunlight. If allergic dermatitis to sunlight occurs after applying cosmetics, discontinue use immediately. If necessary, perform a photopatch test with the suspected allergen. If the cause of the disease can be identified, discontinue contact, and the color of the affected area may gradually fade until the normal skin tone is restored.

There is no effective treatment for melanosis. Patients may take {|###|}compound formula{|###|} vitamin B orally or receive vitamin C injections, and apply 3% hydroquinone cream topically.