An inflammatory process that consists of tiny papules covered by prominent scales and localized typically to the “seborrheic region,” namely, scalp, forehead, eyebrows, malar eminences, paranasal and nasolabial folds, and retroauricular zone, and sometimes the chest and axillary vault.
Seborrheic dermatitis begins as reddish macules that are covered by subtle scale-crusts. In time, slightly elevated papules come into being and they may be associated with scale-crusts that vary in amount from hardly noticeable to striking. Once lesions of seborrheic dermatitis arise, the tendency is for them to wax and wane, but to persist nonetheless for the life of the person who bears them, expanding ever so slightly but relentlessly. The inflammatory process worsens very slowly, but progressively. First it tends to involve the skin above the nasion near the eyebrows, the malar eminences, and the paranasal folds. Over the course of years it may come to involve most of the forehead, the entire malar region, the paranasal and nasolabial folds, the postauricular regions, and the sternum. How extensive seborrheic dermatitis may become cannot be predicted, but it can be foretold that it will not involute in the absence of therapy.
Integration: Unifying Concept
Seborrheic dermatitis is recognizable clinically, not by virtue of study of the individual lesions that compose it, but by virtue of the distribution of those lesions. Sections of tissue of biopsy specimens taken of seborrheic dermatitis, however, show characteristic changes, namely, a superficial perivascular infiltrate of lymphocytes, dilated venules in the upper part of the dermis, slight acanthosis, focal spongiosis in both surface and infundibular epidermis, and scale-crusts that reside especially at lips of infundibular ostia. More longstanding lesions of seborrheic dermatitis, especially those situated over the sternum, show psoriasiform acanthosis and scant spongiosis, in addition to mounds of scale-crust.
Seborrheic dermatitis is a specific type of inflammatory process, distinct from psoriasis. Lesions referred to as sebopsoriasis or seborrhiasis, implying thereby a combination of two diseases, almost always represent either seborrheic dermatitis or psoriasis, not both of them.
The cause of seborrheic dermatitis is not known.
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Scaly, ill-defined plaques on the bridge of the nose, malar region, paranasal region, and chin.
Subtle scaly plaques with scalloped borders on a scalp and forehead. The numerous tan macules are solar lentigines.
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Seborrheic dermatitis: The reddish lesion stopped by furfuraceous scale on the upper lip, nasolabial fold, and malar region are typical of the process.
Seborrheic dermatitis: The ill-defined pink lesions on the forehead, near the eyebrows, the paranasal and nasolabial folds, the malar regions, and the chin are characteristic.
Seborrheic dermatitis: Lesions often involve the “butterfly” (malar) region affected often by lupus erythematosus, as well as the center of the forehead and the region of the eyebrows, the latter not being a site of predilection for lupus erythematosus.
Seborrheic dermatitis: The inflammatory process in the nasolabial fold is characterized by ill-defined redness affiliated with furfuraceous scales.
Seborrheic dermatitis: Ill-defined zones of redness covered by fine scales on the malar region and in the paranasal and nasolabial folds are typical of the disease.
Seborrheic dermatitis: Florid expression with periocular, nasolabial, and perioral involvement by scaly and crusted papules.