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Write this down if your patient has multiple PENS: Look further

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By Warren R. Heymann, MD
June 18, 2016

Papular Epidermal Nevus with Skyline Basal Cell Layer (PENS) was first described by Torrelo et al. They detailed 5 infants with solitary or multiple 1 to 7 mm congenital keratotic papules. Lesions were randomly distributed and did not follow Blaschko lines. They were round, oval, comma-shaped or polygonal. The histologic hallmark was palisaded columnar basal cells with uniform small nuclei, resembling the “skyline” or “eyeliner” sign usually associated with Bowen disease. In this initial series, there were no extracutaneous manifestations (1).

Subsequent reports have included a case of a healthy 13 year-old boy with PENS following Blaschko lines on the clavicle and abdomen suggesting mosaicism (2). Tadini et al recognized that PENS could be part of a neurocutaneous syndrome. In their series of 6 patients, they questioned whether this is distinct syndrome, or a variant of the epidermal nevus syndrome. The authors observed the following:

All but one of our six patients developed neurologic signs and symptoms during the first year of life, in the form of epilepsy and psychomotor delay. Five children had low intellectual performance together with EEG abnormalities and some had MRI changes of the brain. One patient had marked language impairment. The central nervous system involvement had a peculiar benign and self-limiting course and total normalization occurred in one case (3).

Luna et al have just reported 3 additional cases of PENS and have reviewed the literature. All 3 of their patients, aged 7 months to 5 years, had congenital lesions; only the third case demonstrated extracutaneous manifestations, including developmental delay, hypospadias, and a curved penis. All 3 cases were histologically confirmed to be PENS. The authors accrued 16 other patients, including 2 familial cases, from the literature and found that “all patients with extracutaneous manifestations had more than one lesion, but not all patients with multiple lesions had extracutaneous manifestations.” They recommended that patients with more that 4 PENS lesions be referred to a neuropediatrician to exclude mild neurologic delay. (4)

Reading Luna’s article brought back memories of being single at a bar, asking “Where have you been all my life?” or “Haven’t we met somewhere before?” (I hope I used better lines in real life!) In the case of PENS the answer is probably that it is not new, and that I (we) have seen it before — just not recognizing it. In all honesty, I usually do not biopsy epidermal nevi unless there is a compelling reason to do so (such as a change in the lesion, or searching for epidermolytic ichthyosis). The key is to ask the right questions of the parent and/or pediatrician to determine if there is any associated neurologic impairment. If affirmative, it would be appropriate to biopsy such lesions to determine if the histology is consistent with PENS (or another type of epidermal nevus). While a biopsy is not likely to change management, it will help confirm the likelihood of a distinct neurocutaneous syndrome. As more reports come forth, hopefully they will be accompanied by studies that will define this syndrome molecularly.

1. Torrelo A, et al. Papular epidermal nevus with “skyline” basal cell layer (PENS). J Am Acad Dermatol 2011; 64: 888-92.
2. Faure E, et al. Papular epidermal nevus with “skyline” basal cell layer following basal cell layer (PENS) following a Blaschko linear pattern. Pediatr Dermatol 2013: 30: e 270-1.
3. Tadini G. PENS syndrome: A new neurocutaneous phenotype. Dermatology 2012; 224: 24-30.
4. Luna PC, et al. Papular Epidermal Nevus with Skyline Basal Cell Layer (PENS): Three new cases and review of the literature. Pediatr Dermatol 2016: 33: 296-300.

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