Adolescent with rash on face and scalp

Diagnosis: Seborrheic dermatitis

Seborrheic dermatitis (SD) is a chronic dermatitis caused by Malassezia yeast species, including Malassezia (Pityrosporum ovale).¹ SD affects 1% to 3% of the general population in the United States and has 2 incidence peaks: the first occurs during infancy and the second between 30 to 50 years of age.² The abnormal response to the yeast organism leads to inflammation, proliferation, and desquamation.²

There is no cure for seborrheic dermatitis, so the goal of treatment is to control the dermatitis. The diagnosis of SD is made based on the presence of sharply marginated scaled patches in areas with a high concentration of sebaceous glands including the scalp, eyebrows, and nasomesial folds. Pruritus, erythema, and greasy scales also are commonly seen.³ Raised lateral margins reminiscent of the advancing border of dermatophyte infections and postinflammatory hypopigmentation may also be present in African American patients. Both of these findings in the nasomesial folds, eyebrows, and scalp led to the diagnosis of SD in this patient.

Differential diagnosis includes psoriasis, lichen simplex chronicus

The differential for dandruff includes psoriasis, as well as lichen simplex chronicus and tinea capitis. Psoriasis often is associated with thicker, white micaceous scaling. The latter 2 conditions would not produce the symmetrical scaling in nasomesial folds that we saw with our patient.

SD in the central face can appear similar to pityriasis versicolor, allergic contact dermatitis, and irritant dermatitis (pityriasis alba), but these conditions are not associated with diffuse dandruff.