Case of the Week
Section Editors: Matylda Machnowska1 and Anvita Pauranik2
1University of Toronto, Toronto, Ontario, Canada
2BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
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November 7, 2019
Schimmelpenning-Feuerstein-Mims syndrome (SFMS)
- Background:
- SFMS, also known as linear nevus sebaceous syndrome, is a congenital neurocutaneous disorder that is considered to be the best-known form of epidermal nevus syndrome. It is characterized by sebaceous nevi and various ipsilateral extracutaneous anomalies, with the former considered to be a hallmark feature.
- Postzygotic mutations involving HRAS, KRAS, or NRAS genes have been postulated as the cause of this condition.
- Cases are sporadic, thought to be caused by a lethal autosomal dominant mutation that survives by somatic mosaicism.
- Clinical Presentation:
- Characterized by a triad of sebaceous nevi, developmental delay, and seizure disorder with neurologic findings evident in more than half of cases
- The characteristic skin lesion is present at birth in most patients but becomes most conspicuous at puberty, with a predilection for scalp, neck, and face regions.
- Key Diagnostic Features:
- Presence of sebaceous nevi warrants exclusion of this rare disease and serves as an important clue to this condition.
- The other important and commonly associated findings include cutaneous (hyperpigmentation along Blaschko's lines), neurologic (hemimegalencephaly, ipsilateral gyral malformation, corpus callosal or trigeminal lipoma, arachnoid cyst, Dandy-Walker malformation), ophthalmologic (colobomas, choristomas, epibulbar tumors, microcornea), skeletal (vitamin D–resistant rickets, scoliosis, frontal bossing), and vascular anomalies (coarctation of aorta, aortic aneurysm, carotid and/or renal artery stenosis, lymphatic and capillary malformations).
- Bilateral trigeminal nerve lipomas have not been described previously (although unilateral lipomas have been reported).
- Differential Diagnoses:
- Important clues to other epidermal nevus syndromes:
- phacomatosis pigmentokeratotica: sebaceous nevus with papular nevus spilus (checkerboard pattern)
- nevus comedonicus syndrome: ipsilateral cataract
- Becker nevus syndrome: breast hypoplasia; does not follow Blaschko's line pattern
- Proteus syndrome: cerebriform plantar lesions; asymmetric macrodactyly
- Important clues to other epidermal nevus syndromes:
- Treatment:
- Involves multidisciplinary approach; individualized and symptom-directed
- Excision of sebaceous nevi, once considered a favored procedure, is no longer recommended considering the low risk of malignant transformation.
