SEBORRHEIC DERMATITIS
Seborrheic dermatitis is a commonly encountered rash with a bimodal age distribution. There is an infantile and an adult form. The two forms do not resemble each other clinically and are distinct in appearance. The infantile form has also been named “cradle cap” because of its prominent location on the scalp. The adult form has been found in association with many underlying conditions, although it is most commonly seen as an isolated skin finding.
Clinical Findings: The infantile form of seborrheic dermatitis manifests in the first weeks
of life and lasts a few months at most. It affects males and females equally,
and there is no racial predilection. The most usual location of involvement is
the scalp. Most cases are mild and do not cause the parents to seek the advice
of a medical professional. These mild cases manifest with a fine scale that may
be slightly greasy or adherent. The child is unaware of the dermatosis, and it
resolves spontaneously. Rarely, an infant develops greasy yellow, scaly patches
and even plaques across the entire scalp (cradle cap). The dermatitis may
become more inflamed, and weeping from the patches or plaques may ensue. The
infant may try to scratch at the areas, indicating that pruritus is present. In
these severe cases, weeping patches and plaques may also be seen in the groin
and axillary folds. Only in the most exceptional of cases does the rash
disseminate, but it has the ability to affect any region of the body.
The adult version is chronic in nature and affects a
higher percentage of people than does the infantile form. Because of its
chronicity, patients often seek medical advice. There is also quite a bit of
clinical variability in adult seborrheic dermatitis. The face is the most commonly
involved site, with a predilection for the nasolabial fold, eyebrows, ears, and
scalp. It has a strikingly similarity to patches in other locations on the
skin. Most cases are mild and consist of greasy yellow to slightly red, scaly
patches. The scalp involvement is similar in appearance. Seborrheic dermatitis
has a propensity to affect the areas of the skin that have a high density of
sebaceous glands. On occasion, patients have not only facial involvement but
signs of involvement on areas of the upper chest and back.
Many conditions have been associated with the adult
form of seborrheic dermatitis, including Parkinson’s disease and other chronic
neurological disorders. Adult onset of severe seborrheic dermatitis has been
reported to occur with a higher incidence in patients with underlying human
immunodeficiency virus (HIV) infection. HIV-associated seborrheic dermatitis
tends to be wide spread, with
severe facial involvement. Patients who present with severe seborrheic
dermatitis should be assessed for HIV risk factors.
Pathogenesis: The exact
pathogenesis is unknown. Seborrheic dermatitis is believed to be caused by an interaction of various components of
the skin, including the production of sebum, with the normal skin immune system
response to the fungus, Malassezia furfur. The role that each of these
factors plays in the formation of seborrheic dermatitis is not completely
understood.
Histology: Seborrheic
dermatitis is almost never biopsied to confirm the diagnosis. Classic biopsy
specimens show parakeratosis overlying a slightly spongiotic epidermis with a
mild lymphocytic perivascular infiltrate in the dermis. Spores of fungus can be
seen lying on the surface
of the epidermis.
Treatment: Most cases of
infantile seborrheic dermatitis can be ignored or treated with nothing more
than daily baths and a bland emollient. More involved cases can be treated with
more frequent shampooing of the scalp and the use of a mild topical
corticosteroid. The use of ketoconazole cream has also been advocated in some
cases.
Because of its chronic nature, adult seborrheic dermatitis
is treated with topical ketoconazole as a first-line therapy. The other azole antifungal agents are just as
effective. The addition of a weak topical corticosteroid used intermittently
can also lead to excellent results. The scalp is most commonly treated with a
ketoconazolebased shampoo or a tar- or selenium-based shampoo. There is no
cure for seborrheic dermatitis, but most therapeutic regimens, if adhered to,
lead to an excellent clinical response.
