Topical sirolimus therapy for epidermal nevus with features of acanthosis nigricans.

We present a 4-year-old developmentally appropriate boy with short stature and widespread expanding epidermal nevus with features of acanthosis nigricans. He was found to have a mosaic mutation in FGFR3, the R248C variant. Despite several therapies, he continued to have growth, fissuring, and bleeding of the affected skin. Ultimately, topical sirolimus was attempted and found to improve thickness and overall symptoms.