An unusual case of segmental seborrheic keratosis-like keratinocyte epidermal nevus

Sir, Segmental seborrheic keratosis-like keratinocyte epidermal nevus has been rarely described [1]. Its individualization of seborrheic keratosis clinically and histologically remains difficult, especially when it comes to multiple segmental seborrheic keratosis. However the evolution and the date of appearance of lesions constitute the most guiding element. Segmental seborrheic keratosis may be a possible variant of keratinocyte epidermal nevus developed after birth along the Blaschko’s lines [2], since in both types of lesions, the same genetic mutation may be present (in particular, of FGFR3 and PIK3CA) [3]. A 12-year-old girl with no particular history was referred to our dermatologic department for the presence of multiple small pigmented lesions with right periocular arrangement. The oldest lesion of had been evolving since birth, gradually increasing in size. The other lesions have appeared since the age of 7 years. Clinical examination revealed the presence of a 15 mm brownish well-limited plaque with a slightly infiltrated base and verrucous surface. The other lesions are millimetric papules sharing the same characteristics as that described above and arranged along a segmental course (Fig. 1). The lesions were asymptomatic. Dermoscopic examination excluded the melanocytic nevus for the absence of the classic network while revealing a seborrheic keratosis-like pattern characterized by the presence of typical multiple milia-like cysts and comedo-like openings (Fig. 2). The histological examination showed orthokeratosis hyperkeratosis above a hyperacanthosic epidermal with broad papillomatosis and intraepidermal invaginations and focal basal hyperpigmentation (Fig. 3). A diagnosis of segmental seborrheic keratosis-like keratinocyte epidermal nevus (SSKKEN) was made and the patient underwent ablative laser treatment with favorable progress. Our case is special due to the rarity of the seborrheic keratosis-like keratinocytic epidermal nevus, and its recognition is also of great interest in the therapeutic choice, replacing surgery with laser treatment.Figure 1: Clinical aspect showing brown papules and their segmental distribution.Figure 2: Dermoscopic features showing comedo-like openings, ridges, and fissures.Figure 3: Histological finding showing large papillomatosis and invaginations filled with keratin creating horning pseudo globes and focal basal hyperpigmentation (Hematoxylin-eosin stain×50).Acknowledgements None. Declaration of patient consent: The authors certify that they have obtained all appropriate patient consent forms. In the form, the parent has given consent for images and other clinical information to be reported in the journal. The parent understands that names and initials will not be published and due efforts will be made to conceal patient identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Funding source: None. Ethics approval: NA. Patient consent: Taken. Conflicts of interest There are no conflicts of interest.