Epidermal Nevus Syndrome

Overview

Epidermal nevi (EN) are congenital hamartomas of embryonal ectodermal origin classified on the basis of their main component; the component may be sebaceous, apocrine, eccrine, follicular, or keratinocytic. An estimated one third of individuals with epidermal nevi have involvement of other organ systems; hence, this condition is considered to be an epidermal nevus syndrome (ENS). 

http://emedicine.medscape.com/article/1117506-overview