Chapter 2. Sebhorreic Dermatitis
Seborrheic dermatitis is a chronic inflammatory disorder most commonly seen in infants and adolescents, paralleling the activity of the sebaceous glands. In infants, the disorder is most common within the first 4 to 6 weeks of life but may occur up to one year of age. Seborrheic dermatitis is characterized by a symmetric, red scaling eruption that occurs primarily in intertriginous and hair-bearing areas such as the scalp, eyebrows, posterior auricular area, neck, axilla and groin. Infants with seborrhea commonly manifest the disorder as “cradle cap” with greasy, salmon-colored scale on the vertex of the scalp (PICTURE A). In some cases, seborrhea may cause chronic, persistent scalp or diaper dermatitis and may be difficult to distinguish from infantile psoriasis. Less commonly, infants will progress to very severe disease with whole-body, almost confluent involvement (PICTURE B). In seborrheic dermatitis, Candida albicans commonly invades the areas of macerated skin, exacerbating the dermatitis.
The etiology of seborrheic dermatitis is unknown although a few studies have indicated that the fungal organism Pityrosporum ovale (Malassezia furfur) plays a role. In these studies the fungus was cultured in the majority of the seborrhea patients, but in very few control patients. In one study, treatment with ketoconazole resulted clinical cure in two-thirds of infants treated. However, these studies are controversial since M. furfur in other studies have been found to be part of the normal flora in healthy individuals.
Diagnosis is generally a clinical one. Skin biopsy may be helpful but is not diagnostic in most cases.
The majority of cases of infantile seborrheic dermatitis will resolve spontaneously, and the disorder tends not to recur. When necessary to treat, patients respond nicely mild tar shampoos, oatmeal baths and low-potency topical steroids. Topical anti-fungals are often prescribed in more severe cases, given the current data regarding the role of Pityrosporum. A poor response to corticosteroids or the presence of atypical findings (petechiae, purpura, lymphadenopathy, organomegaly, poor growth or diarrhea) are not consistent with uncomplicated seborrheic dermatitis and should prompt further evaluation for metabolic, immune and neoplastic disorders, particularly Langerhans’ cell histiocytosis.
In adolescents the eruption of seborrheic dermatitis is generally much more localized and is often confined to the scalp and intertriginous areas. Almost all patients have scalp scaling. Blepharitis, along with involvement of the naso-labial folds and posterior auricular areas may also be seen. Frontal hairline scale may be seen similar to that of psoriasis. Loss of hair is not uncommon. The rash tends to be only mildly pruritic, if at all. Anti-seborrheic shampoos (selenium, sulfur, zinc pyrithione or salicylic acid) and low-potency topical corticosteroids may be helpful. Patients often require the continued use of an antiseborrheic shampoo for control, with or without a topical antifungal agent.
Seborrhea is a common cutaneous manifestation of acquired immunodeficiency syndrome (AIDS) in adolescents and should be considered in patients with risk factors who have severe or atypical dermatitis.