Child With “Distressing” Problem

ANSWER
The correct answer is nevus sebaceous (choice “a”). This benign hamartomatous lesion is derived from local tissue and grows at the same rate.

It differs considerably from the other items in the differential, including aplasia cutis congenita (choice “b”). In this condition, a focal area of epidermis simply fails to develop, leaving a permanent hairless scar that contrasts sharply with the raised, mammillated plaque of nevus sebaceous.

Epidermal nevus (choice “c”) is usually a collection of tan to brown superficial nevoid papules that can be linear, agminated, or plaque-like. These lesions lack the color and mammillated surface of those seen in nevus sebaceous.

Neonatal lupus (choice “d”) can present at birth with hairless, cicatricial inflamed lesions. However, these tend to resolve quickly, often leaving focal scarring alopecia but no plaque formation.

DISCUSSION
Nevus sebaceous (NS), first described by Jadassohn in 1895, has long been recognized as an unusual but by no means rare congenital lesion. Occurring equally in both sexes and comprising ­sebaceous glands in a nevoid morphologic context, NS is considered a variant of sebaceous nevi and verrucous epidermal nevi in some circles. All three are derived from overgrowth of local, normal tissues that typically grow at the same rate as surrounding structures.

The vast majority of NS lesions are found in the scalp, although they can also develop on the ear or neck and, rarely, elsewhere on the body. This patient’s plaque—with its uniform surface; tiny, smooth, shiny papules; and (perhaps most important) total lack of hair—is typical. Other classic features are congenital onset and permanent nature, which distinguish them from the rest of the differential.

Focal malignant transformation of NS lesions has been reported—in fact, this author has seen two such cases in 30 years. Both were small basal cell carcinomas, although cases of melanoma and other malignancies have been reported.

Such changes are rare enough that most experts consider prophylactic removal to be unwarranted. Watching the lesions for change over the years is certainly reasonable, as is protecting them from sun exposure.

Surgical removal—usually performed by a plastic surgeon—is occasionally necessary for cosmetic reasons. This is particularly so when NS covers a portion of the face, or when the cosmetic implications of having a hairless plaque in the scalp are sufficiently distressing.

This patient and her parents were educated about the nature of the diagnosis and apprised of their options.

Editor's note: For a similar presentation with a very different diagnosis, see the March 2015 DermaDiagnosis case (http://bit.ly/1ye69Ym).