Track: Case Reports

Abstract:

Epidermal nevus syndrome (ENS) refers to a diverse group of disorders characterized by the presence of epidermal nevi (EN) in association with extracutaneous abnormalities. Recognized subtypes include Schimmelpenning syndrome, CHILD syndrome, and others. ENS is often caused by postzygotic mosaic mutations, particularly in genes of the RAS/MAPK pathway, classifying it among mosaic RASopathies. We present a 7-month-old infant evaluated for congenital scalp cutis aplasia with a characteristic hair collar sign, multiple linear blaschkoidal plaques distributed across both arms, shoulders, and back, and a telangiectatic hemangioma present since birth. Histopathological evaluation revealed subtle papillomatosis, compact hyperkeratosis, and hypergranulosis involving the eccrine and follicular ostia. Focal eccrine squamous syringometaplasia was also noted. The presence of multiple EN, benign hamartomatous lesions often following Blaschko's lines, along with cutis aplasia, raises suspicion for a mosaic neurocutaneous syndrome, as these lesions can be associated with somatic mutations in genes such as FGFR3, PIK3CA, or KRAS, and are often accompanied by extracutaneous involvement. Genetic testing identified a somatic BRAF mutation consistent with a postzygotic somatic origin. Continued dermatologic surveillance was recommended. This case highlights the subtle and nonspecific histopathologic findings of early EN. Unlike the classical histologic features, early manifestations can be easily overlooked. Therefore, careful clinicopathologic correlation is essential for timely diagnosis. In our case, the clinical presentation was consistent with ENS, with subtle changes, particularly involving the follicular ostia, that raised concern for evolving EN and served as early diagnostic clues in the absence of typical features.

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James Curry