Typical lesions of nevus sebaceous are faintly notable to erythematous inflammed papules and plaques with alopecia present at birth or noted early in life. Lesions are responsive to maternal hormone stimulation accounting for the inflammation which usually resolves over several months. Many parents do not seek medical attention for this birthmark because the improvement noted early in life suggests that the birthmark will spontaneously involute. Despite this, lesions are persistent and develop into a yellow brown or orange pink flat velvety plaque. The alopecia is also persistent.
Lesions enlarge over time, growing with the patient.
At puberty the hormones that stimulate pubertal changes result in thickening, erythema and nodularity in these lesions, similar to that noted a birth. Papillomatous or wart-like projections are also quite common beginning at puberty. These neoplasms generally occur during adolescence or adult life. The development of a rapidly enlarging papule within nevus sebaceous or of ulceration within the plaque may portend malignant degeneration. Appearance of these changes warrants immediate biopsy.