Nevus sebaceus typically is caused by a sporadic mutation, though familial cases have been reported.1 Additionally, germline HRAS mutations can lead to Costello syndrome, an autosomal-dominant disorder characterized by short stature; intellectual disabilities; coarse facial features; facial and perianal papillomata; cardiac defects; loose skin; joint hyperflexibility; and an increased risk for malignant tumors including rhabdomyosarcoma, neuroblastoma, and transitional cell carcinoma of the bladder.6
The diagnosis of NS often can be made clinically but can be difficult to confirm in underdeveloped lesions in young children. The differential diagnosis can include alopecia areata, aplasia cutis congenita, juvenile xanthogranuloma, epidermal nevus, de novo syringocystadenoma papilliferum, and solitary mastocytoma.1 Nevus sebaceus can be associated with 4 additional syndromes: Schimmelpenning syndrome; phacomatosis pigmentokeratotica; didymosis aplasticosebacea; and SCALP (sebaceus nevus, central nervous system malformations, aplasia cutis congenital, limbal dermoid, pigmented nevus) syndrome.1 Approximately 7% of NS cases may be associated with Schimmelpenning-Feuerstein-Mims (SFM) syndrome, a more severe condition that leads to systemic involvement and abnormalities in the neurological, ophthalmological, cardiovascular, genitourological, and skeletal systems.1,3 Phacomatosis pigmentokeratotica has speckled lentiginous nevi, as well as abnormalities in the neurological, ophthalmological, cardiovascular, genitourological, and skeletal systems.1 Didymosis aplasticosebacea is the concurrence of NS and aplasia cutis congenita.
The definitive treatment of NS is surgical excision. Alternative therapies include photodynamic therapy, fractional laser resurfacing, and dermabrasion; these are not definitive treatments, and patients must be monitored for the development of secondary neoplasms. Multiple variables must be considered when determining treatment, including patient age, risk potential for malignancy, and surgery-associated risks.1 In our patient, given the extent of the lesions, active observation and follow-up was agreed upon for management.
This case demonstrates the importance of considering NS as an alternative diagnosis when alopecia areata has been diagnosed in a child who is unresponsive to treatments. After the diagnosis of NS is confirmed, more serious associated syndromes should be ruled out, and treatment should be tailored to each case.