Epidermolytic hyperkeratosis: clue for diagnosis

Verrucous epidermal nevi are congenital, non-inflammatory cutaneous hamartomas caused by somatic mosaicism. Histologically, epidermal nevi show hyperkeratosis, hypergranulosis, acanthosis, and papillomatosis with or without inflammation. Epidermolytic hyperkeratosis is a rare occurrence. We report a case of an epidermolytic variant of systematized verrucous epidermal nevus, involving large areas of the body. Correspondence to: Damevska Katerina, Clinic of Dermatology, Medical Faculty, University “Ss Cyrilius and Methodius”, Skopje, Republic of Macedonia, E-mail: kate_damevska@yahoo.com


Introduction
Verrucous epidermal nevus (VEN), also known as keratinocytic or non-organoid epidermal nevus, is a congenital, non-inflammatory cutaneous hamartoma composed of keratinocytes. It is manifested as papillomatous papules or plaques, often linear or Blaschkoid in shape. The extent and distribution of the VEN as well as the presence or absence of inflammation determines its subtype: localized VEN, inflammatory linear verrucous epidermal nevus (ILVEN), nevus uniuslateralis, systematized VEN, and ichthyosis hystrix [1].
The term systematized epidermal nevus is used for lesions that are bilateral and excessive. Ichthyosis hystrix is a term used to describe several rare skin disorders in the ichthyosis family of skin disorders characterized by massive spiky or verrucous hyperkeratosis. Histologically, VEN show hyperkeratosis, hypergranulosis, acanthosis, and papillomatosis with or without inflammation. Epidermolytic hyperkeratosis is a rare occurrence [2].
We report a case of an epidermolytic variant of systematized verrucous epidermal nevus, distributed along Blaschko lines.

Case report
A 1-year-old female child presented with widespread, dark-brown, hyperkeratotic, verrucous plaques since she was one month of age. There was no history of blisters or generalized redness at or after birth. Family history was notable for parental consanguinity (third cousins). However, no other family members, including three half sisters were affected by a similar skin condition.
Upon examination, dark-brown, verrucous plaques in Blaschkoid distribution were noted on the trunk and extremities bilaterally ( Figure  1a). Over the thorax, linear plaques ran transversely, arranged in streaks and whorls (Figure 1b), as well as linear streaks over both lower limbs. Hyperpigmented velvety plaques were present in the intertriginous areas. The diaper area, and central face, as well as parts of truncus were spared. The hair, nails, and oral cavity were normal. Detailed pediatric, orthopedic and neurological consultations were sought and revealed no abnormalities.
Through light microscopy, epidermolysis is seen as various sized clear spaces around keratinocyte nuclei (perinuclear vacuolisations) with indistinct peripheral cell boundaries in the upper spinous and granular layers. The boundaries appear to be formed by eosinophilic and basophilic granules [6].
The use of the term epidermolytic hyperkeratosis to describe both the clinical disease and the characteristic histopathologic features caused great confusion in medical literature.
More recently, there are attempts in order to differentiate clinical epidermolytic hyperkeratosis (cEHK) and histologic epidermolytic hyperkeratosis (hEHK). The histology of EHK is seen in a spectrum of clinical conditions including generalized epidermolytic hyperkeratosis, also known as bullous congenital ichthyosiform erythroderma, mosaic cEHK, ichthyosis bullosa of Siemens, and Vorner's palmoplantar keratoderma Furthermore, hEHK is seen in a variety of other conditions including melanocytic nevus, basal cell carcinoma, pilar cyst, leukoplakia, epidermolytic acanthoma and nevoid follicular epidermolytic hyperkeratosis, as well as in normal skin and in normal oral mucosa.
According to Ross et al, the pattern of histologic involvement may be a useful predictor of the clinical phenotype of cEHK: the continuous involvement of the entire horizontal epidermis correlates with generalized cEHK, while focal EHK correlates with mosaic epidermolytic hyperkeratosis. Our case revealed both histological patterns, focal and continuous.
Management of VEN is challenging.Topical modalities have shown inconsistent efficacy, and destructive methods, including laser, electrocoagulation, and dermabrasion, have potential permanent complications. Definitive treatment involves full-thickness excision, which may not be possible in extensive lesions [7]. Taking into account the young age of our patient, our main treatment goal was the reduction of hyperkeratosis.

Conclusion
A rare subgroup of epidermal nevi displays histopathological features typical of EHK. Clinicopathologic correlation is essential for diagnosis.