A congenital, hairless plaque consisting of overgrown epidermis, sebaceous glands, hair follicles, apocrine glands and connective tissue. They are a variant of epidermal naevi. Sebaceous naevi most often appear on the scalp, but they may also arise on the face, neck or forehead. At birth, a sevaceous nevus typically appears as a solitary, smooth, yellow-orange hairless patch. Sebaceous naevi become more pronounced around adolescence, often appearing bumpy, warty or scaly.