Papular epidermal nevus with "skyline" basal cell layer (PENS) is a very rare type of keratinocytic nevus and is associated with extracutaneous findings such as neurological symptoms in about 50% of the cases. Therefore, it is also referred to as PENS syndrome. Clinically visible hyperkeratotic papules and plaques already appear at birth or shortly thereafter, while neurological symptoms such as epilepsy and mental retardation manifest themselves during childhood. Genetics suggests gonadal mosaicism as a possible cause for the disease. Another hypothesis is that genetic mutation can occur in a mendelian trait or through a paradominant inheritance.

Papular epidermal nevus with skyline basal cell layer (PENS) is a newly described keratinocytic nevus whose dermoscopic characteristics have not been clarified. We used a dermatoscope to investigate the multiple PENSs of a patient with PENS syndrome. All the lesions shared a common dermoscopic homogeneous white pattern surrounded by peripheral, slightly dotted hyperpigmentation. The smallest lesions had no other features, whereas the largest lesions had some scaling, directly proportional to their dimension, and a central, clear, pink discoloration.