Fig. 16.1
Upper panel demonstrates an older woman with diffuse, whitish scaling of her scalp secondary to erythrodermic psoriasis. Lower panel demonstrates mild erythema and diffuse scaling secondary to pemphigus foliaceous that may be confused for scaly scalp. Closer inspection revealed superficial erosions beneath the keratinaceous material
Case
A patient presents with scaly scalp.
Differential Diagnosis
includes four common disorders
pityriasis capitis (known as dandruff and in the distant past as “seborrhea sicca”)
seborrheic dermatitis
psoriasis, and
tinea capitis’
two rare disorders
dermatomyositis and
acute Langerhan cell histiocytosis
and two disorders that are not definitively distinct but instead are morphological descriptive terms
sebopsoriasis and
tinea amiantacea
Clinical Clues
Dandruff or pityriasis capitis is among the most common skin disorders and is easily recognized by a dry, flaky scalp. The disorder has been thought to be due to abnormality in sebaceous glands for over a century, hence the old term “seborrhea sicca,” and should be distinguished from seborrheic dermatitis, a related disorder but with oily or greasy scaling. Both disorders may be pruritic and are believed to be due to infection with Malassezia. Both respond to the same treatment, which is why patients with dandruff are labeled by dermatologists as having seborrheic dermatitis. Younger generations of dermatologists may not even recognize dandruff as a separate disorder from seborrheic dermatitis.
Dandruff consists of generally diffuse, fine, dry, flaky scaling, while seborrheic dermatitis reveals mild erythema and glistening greasy scale. Although dandruff is a phenomenon of the scalp, seborrheic dermatitis may involve multiple sites over the face, ears, anogenital skin, mid-chest, mid-back, and skin folds. It is easiest to recognize over the face. When it involves skin folds, it may be mistaken for intertrigo .
Face lesions in dark-skinned individuals, especially African-Americans, may be annular and be confused for other disorders, including sarcoidosis and discoid lupus erythematosus (DLE).
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