Nevus sebaceous syndrome is a rare, congenital condition identified by a nevus sebaceous birthmark. This developmental disorder can be associated with abnormalities in other body systems. It arises from a defect in the ectoderm, the embryonic layer that gives rise to both skin and nervous tissue. The condition is not inherited but occurs sporadically due to genetic changes within certain cells during embryonic development.
The Hallmark Skin Lesion
The nevus sebaceous is a birthmark, often appearing at birth or during early childhood. It presents as a solitary, hairless patch or plaque. In infants and young children, the lesion is smooth or velvety, with a yellow-orange to pinkish color.
Commonly found on the scalp, face, or neck, these lesions can vary in size from a few millimeters to several centimeters. If located on the scalp, the nevus sebaceous creates a well-defined area where hair does not grow. The nevus’s appearance can change over time, especially around puberty.
During adolescence, hormonal influences can cause the lesion to become more pronounced, thickening and developing a warty or bumpy texture. This evolution mirrors the maturation of normal sebaceous glands in the skin. A nevus sebaceous is classified as a hamartoma, an overgrowth of normal skin components like sebaceous glands, hair follicles, and epidermal tissue, but in a disorganized manner.
Beyond the Skin: Associated Conditions
While the nevus sebaceous is the primary feature, the syndrome involves potential abnormalities in other body systems. Not all individuals with a nevus sebaceous will develop these associated conditions, and their severity can vary significantly. When systemic involvement is present, the condition may also be referred to as Schimmelpenning syndrome or Organoid Nevus Syndrome.
Central Nervous System (CNS) involvement is among the most common extracutaneous anomalies. This can include neurological issues such as seizures, which are common. Developmental delays and intellectual impairment are also observed. Structural brain abnormalities, such as hemimegalencephaly (enlargement of one side of the brain) or cortical malformations, may also occur.
Ocular (eye) abnormalities are another common association. These can manifest as structural issues like colobomas (gaps or defects in parts of the eye) or ocular lipodermoids (fatty growths on the eye surface). Other eye findings include retinal anomalies, strabismus, or cataracts.
Skeletal system involvement is less common but can occur. Rarely, individuals may present with bone abnormalities such as bone cysts or scoliosis (spinal curvature). Other rare associations can include involvement of the endocrine, cardiovascular, or urogenital systems.
Diagnosis and Ongoing Care
Nevus sebaceous syndrome is diagnosed through a combination of clinical observation and specialized investigations. The characteristic appearance of the nevus sebaceous often allows clinical diagnosis by visual inspection, especially in childhood. If there is any uncertainty, a skin biopsy can confirm the diagnosis by examining tissue under a microscope.
When systemic involvement is suspected based on symptoms or physical examination, further investigations are important. This may include imaging studies such as MRI or CT scans of the brain to detect structural abnormalities. Ophthalmological examinations assess for eye abnormalities, and neurological evaluations help identify and manage conditions like seizures or developmental delays.
Surgical excision of the nevus sebaceous is a common management approach. This is often recommended for cosmetic reasons, particularly if the lesion is large or located in a prominent area. Excision also helps mitigate the small risk of developing secondary tumors within the lesion, which are usually benign but rarely malignant, especially after puberty.
Long-term follow-up and multidisciplinary care are important, especially for individuals with or at risk for systemic manifestations. This involves regular check-ups with various specialists, such as neurologists, ophthalmologists, or orthopedists, depending on the specific associated conditions. The goal is to monitor for any new developments or changes and provide timely intervention and support.