Papular Epidermal Nevus with “Skyline” Basal Cell Layer Syndrome – Natural Course: Case Report and Literature Review

Abstract

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.

Familial papular epidermal nevus with “skyline” basal cell layer

“…A report by Brena et al included a mother and son with isolated skin manifestations. Recently, Zahn et al reported 2 brothers with cutaneous PENS lesions and neurologic symptoms only in the younger brother.…”

“…Different theories have been proposed to explain familial occurrence of PENS, such as gonadal mosaicism or inheritance in a mendelian trait, although paradominant inheritance has been postulated as the most likely . Torrelo et al performed genetic testing of lesions from two children of his series but failed to identify any hotspot mutation in the fibroblast growth factor receptor 3 (FGFR3) and phosphatidylinositol 3‐kinase catalytic alpha (PIK3CA) genes, which are often present in common keratinocytic nevi.…”

“…PENS may appear in association with extracutaneous manifestations, mainly neurologic . Only three cases of familial PENS have been reported . We describe another case of familial PENS.…”

Hypopigmented Papules in Infancy: A Diagnostic Challenge: Answer

“…3,4 PENS most commonly presents as asymptomatic, small, round or polygonal hyperkeratotic papules or plaques. The color of lesions can range from white to brown, [4][5][6]10,13 and in some cases, lesions of different color may be present in the same individual. 7,10,11 Unlike epidermal nevi that occur linearly along lines of Blaschko, 4 PENS lesions do not typically follow a similar distribution and mostly occur in a sporadic distribution, with a predilection for the face, neck, trunk, and extremities, while sparing the palms and soles.…”

“…further 5 cases having developed PENS lesions within their first year of life. [2][3][4][5][6][7][8][9][10][11][12][13] In 2 cases, the exact age of development had not been reported. 6,10,11 New lesions can develop within months or up to 3 years after onset, and the total number may go up to as high as 18.…”