Linear nevus sebaceus syndrome

Linear nevus sebaceus syndrome, also known as Schimmelpenning syndrome or Schimmelpenning-Feuerstein-Mims syndrome, is a rare neurocutaneous disorder characterized by the presence of a sebaceous nevus (a yellowish, waxy, hairless plaque typically located on the face or scalp) in association with abnormalities of the central nervous system, eyes, and skeletal system. The condition is classified among the epidermal nevus syndromes and is thought to arise from postzygotic somatic mutations, most commonly involving the HRAS or KRAS genes, leading to mosaic distribution of affected cells. The hallmark feature is a linear sebaceous nevus present at birth, which follows the lines of Blaschko. Neurological manifestations may include seizures (often infantile spasms), intellectual disability, and structural brain abnormalities such as hemimegalencephaly. Ocular findings can include colobomas, lipodermoids, and other developmental anomalies of the eye. Skeletal abnormalities such as vitamin D-resistant rickets, hemihypertrophy, and bone cysts may also occur. Additional features can include cardiac defects and vascular malformations. Treatment is symptomatic and multidisciplinary. Seizures may require antiepileptic medications and, in refractory cases, neurosurgical intervention such as hemispherectomy. The sebaceous nevus itself carries a small risk of secondary neoplastic transformation (most commonly trichoblastoma or basal cell carcinoma) and may be surgically excised for cosmetic or preventive reasons. Ophthalmologic, orthopedic, and developmental support are important components of long-term management. Regular monitoring by a multidisciplinary team including dermatology, neurology, ophthalmology, and genetics is recommended.

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