The specific symptoms and severity of nevus sebaceus syndrome can vary greatly from one person to another. It is important to note that affected individuals may not have all of the symptoms discussed below. Affected individuals or their parents should talk to their physician and medical team about their specific case, associated symptoms and overall prognosis.
The characteristic skin lesion that affects individuals with nevus sebaceus syndrome is a sebaceous nevus, which is a type of epidermal nevus. The scalp, neck and face are most often affected. The arms, legs and trunk may also be affected. Sebaceous nevi are usually salmon or yellowed colored, hairless, smooth patches. Eventually (usually around puberty) they become more pronounced and may appear scaly, warty or thickened. When the scalp is involved, large Lesions may be present with associated areas of hair loss (alopecia). Sebaceous nevi may be prominent and easily noticeable at birth or be subtle and unrecognized. Sometimes, sebaceous nevi do not become apparent until after puberty when they go through the above mentioned changes. The lesions, apart from their appearance, usually do not cause additional symptoms.
Nevus sebaceous most often occurs as isolated finding and usually is not associated with any abnormalities in other organs. However, when it occurs with additional extra-cutaneous symptoms, the term, nevus sebaceus syndrome, is appropriate. Some researchers have noted that central facial epidermal nevi may be more likely to be associated with malformations of the brain, eyes and cranial bones.
Neurological abnormalities often occur in individuals with nevus sebaceus syndrome including seizures, delays in attaining developmental milestones (developmental delays), intellectual impairment, damage to certain cranial nerves and abnormalities affecting certain structures of the brain. Such abnormalities include one side of the brain being larger than the other (hemimegalencephaly), malformation (dysplasia) of the certain brain vessels, absence (agenesis) of the bundle of nerves that connects the two cerebral hemispheres (corpus callosum), and defects of the folds of the brain including a smooth brain that lacks the distinctive folds (agyria), abnormally small folds (microgyria) and abnormally thickened folds (pachygyria).
Individuals with nevus sebaceus syndrome may also have Dandy-Walker malformation, a rare malformation of the brain that is present at birth (congenital). It is characterized by an abnormally enlarged space at the back of the brain (cystic 4th ventricle) that interferes with the normal flow of cerebrospinal fluid through the openings between the ventricle and other parts of the brain (foramina of Magendiand Luschka). Excessive amounts of fluid accumulate around the brain and cause abnormally high pressure within the skull, Swelling of the head (congenital hydrocephalus), and neurological impairment. Motor delays and learning problems may also occur. Dandy-Walker malformation is a form of “obstructive” or “internal noncommunicating hydrocephalus”, meaning that the normal flow of cerebrospinal fluid is blocked resulting in the widening of the ventricles. Dandy-Walker malformation is often associated with partial agenesis of part of the cerebellum known as the cerebellar vermis.
Ocular abnormalities also occur in nevus sebaceus syndrome including a partial absence of tissue (coloboma) from the colored portion of the eye (iris) or the membrane lining the back of the eyes (retina), clouding (opacity) of the cornea, crossed eyes (strabismus), defects of the optic nerve and scarring degeneration or detachment of the retina. Some individuals may have a benign, yellowish-white, fatty tumor on the outer portion of the eyeball (epibulbarlipodermoid). A sebaceous nevus on the face can potentially involve structures in the eye including the eyelids and the thin, clear membrane that covers the outer surface of the eye (conjunctiva).
Affected individuals may also have skeletal malformations including abnormal curvature of the spine, dislocation of the hip, and deformities of the limbs. Craniofacial defects such as an unusually prominent forehead (frontal bossing), underdeveloped nasal and orbital bones and asymmetry of the skull may also occur. Additional skeletal malformations may include bone cysts, underdevelopment of the pelvis and incomplete formation of certain bony structures including the ankle, foot and bones of the spinal column (vertebrae).
Individuals with nevus sebaceus syndrome may also develop vitamin D-resistant rickets, a condition characterized by bow deformities of the legs, Pain in the legs and progressive softening of the bone structure. In children, growth rates may be slow, ultimately resulting in short stature. Affected individuals may be prone to fractures.
According to the medical literature, sebaceus nevi are associated with an increased risk of developing secondary benign skin tumors such as trichoblastoma or syringocystadenomapapilliferum, whereas malignant secondary tumors (basal cell carcinoma, squamous cell carcinoma, sebaceous carcinoma) arising in association with a sebaceous nevus are very rare.