Sebaceous naevi are also called organoid naevi because they may include components of the entire skin organ. They consist of overgrown epidermis (upper layers of the skin), sebaceous glands, hair follicles, apocrine glands and connective tissue.
Sebaceous naevi most often appear on the scalp, but they may also arise on the face, neck or forehead. Lesions are always present at birth and do not spread during childhood. However, they become more raised at puberty or earlier.
A sebaceous naevus is at first a solitary smooth yellow-orange hairless patch. Sebaceous naevi become more pronounced around adolescence, often appearing bumpy, warty or scaly. Neurological disorders are rare, but occasionally occur in children with very large sebaceous naevi. Epileptic seizures are the most common problem.
Sebaceous naevus syndrome refers to the association of a large sebaceous naevus with disorders of the eye, brain and skeleton, but this is extremely rare. There may be eye tumours and/or the skull may be asymmetrical. Characteristic associated neurological features may include:
Developmental delay.
Seizures, especially infantile spasms.
Hemiparesis (paralysis of half the body) or cranial nerve palsies (paralysis of individual nerves).
X-ray images and ultrasound evaluation may be quite normal.
Various structural abnormalities may rarely be found within the brain. Most sebaceous naevi remain unchanged in adulthood and do not cause any problems.
Removal or excision is the best treatment.