Nevus comedonicus (NC) is a rare type of epidermal nevus with predilection for the face and neck area. The condition develops within the first decade of life in most patients. NC is characterized by dilated, plugged follicular ostia containing lamellar keratinaceous material and grouped in a honeycomb pattern; the distribution of lesions may be unilateral, bilateral, linear, interrupted, segmental, or along the lines of Blaschko. NC may be nonpyogenic with an acne-like appearance or associated with the formation of cysts, papules, pustules, and abscesses. Histologically, the lesions are large, grouped, dilated follicular ostia devoid of hair shafts but filled with keratin layers (summary by Tchernev et al., 2013). [from
OMIM]