1.1.2.5 Seborrhoeic Dermatitis

Seborrheic dermatitis is a very common disease in different ages. About 5% of the population needs treatment. In infants, it starts during the first three months and may persist up to 12 months. It may be seen later in the 4th to 7th life decade. All ethnic groups are involved.

Seborrheic dermatitis is a chronic recurrent inflammatory dermatitis with yellow-white fine to moderate scaling on an erythematous background which may involve the face, scalp and other seborrheic areas of the body.

The exact aetiopathogenesis of seborrheic dermatitis is not fully known. A genetic background has yet not been found. Seborrhoea (oily skin) seems to play an important role and localisation in the areas rich in sebaceous glands is a predisposing factor. It is very important that an increased colonization of seborrheic areas by the commensal lipophilic yeast Malassezia furfur and spp. (formerly called Pityrosporum ovale) can be found. In newborn children, stimulation by a short temporary androgen availability is another cause. It may also be seen in patients who are severely immunocompromised, often as a HIV/AIDS-related dermatosis. Furthermore, it may be related to nutritional deficiencies, a subnormal or pathologic blood level of biotin (vitamin H), folic acid, selenium or zinc. Combination of these deficiencies can be found.

The main clinical feature is a pityriasiform scaling on an inflammatory, erythematous skin accompanied by itch. Often the patients scratch and irritation can be found. In infants, the so-called cradle cap is yellowish oily scales, which may be itchy and lead to scratching, depending of the age of the child.

The two manifestations of seborrhoeic dermatitis are:

• The Early type in infants usually appearing in the first 3 months of life and involving scalp and sometimes intertriginous areas.

• The Adult type which also involves the seborrheic areas, however, the intertriginous areas are not involved and are an important differential diagnosis of intertriginous psoriasis.

More severe manifestations and courses can be seen with HIV /AIDS patients.

Sometimes a deficiency of folate, biotin, selenium or zinc in blood can be detected and should be substituted and the causes need to be followed up.

There is no specific dermatopathologic pattern of seborrheic dermatitis. Usually hyper- and parakeratosis of the interfollicular epidermis and the infundibulum of the hair- and sebaceous follicles can be seen. Crusts with serum influx in the stratum corneum and spongiosis in the spinous layers can be found. Typically, no Munro abscesses are associated with seborrheic dermatitis, and, if found, are a sign of overlap with psoriasis (so called seborrhiasis) or psoriasis itself.

The course of the disease is variable in degree. It worsens with stress of different origin, can be provoked or even improved by UV light. Heavy colonisation may occur with M. furfur, the reservoir of which is in general the scalp (openings of sebaceous and hair follicles). In addition, excessive washing procedures, inappropriate local irritating topical ointments, alkaline pH, mechanic irritation and sweating all worsen the course of the disease, which in general is unpredictable.

The most important complication is an overlap with psoriasis. Sometimes a superinfection with S. aureus may occur, and, rarely either a toxic-irritant or an allergic contact dermatitis may develop.

A diagnosis can easily be made by the presence of an oily skin, pityriasiform desquamation, typical clinical features and a distribution in the nasal folds, lateral fold of the mouth, glabella and sternal region.

The most important differential diagnosis in adults is a manifestation of psoriasis in the face and scalp. In childhood and in particular in infants, atopic dermatitis has to be excluded.

The reduction of Pityrosporum spp colonisation with topical imidazoles, mild keratolytic agents or topical zinc pyrithione is essential. Washing of the hair at least every other day with antimycotics in particular ketoconazol to avoid relapses is necessary. Topical zinc oil, especially in newborns, seems to be the most promising. Salicylic acid should be avoided in infants. Short-term mild topical corticosteroids combined with clotrimazole can be used.

Recently, a topical phosphodiesterase 4 inhibitor 0.3% foam has been launched.

Evidence for alcohol abuse in the history has to be considered (malnutrition).