Porcupine skin: A rare case of verrucous epidermal nevus

A 9-year-old female, born to second-degree consanguineous parents, presented with asymptomatic, progressively thickening, hyperpigmented, raised lesions over the body since birth, sparing the face. Cutaneous examination revealed multiple well-defined verrucous papules and plaques arranged in linear and serpiginous patterns along Blaschko’s lines over the trunk and extremities [Figure 1a and b]. The lesions were bilaterally symmetrical and systematized, with sparing of the face and palmoplantar surfaces. They were firm, rough, and non-tender, without erythema or scaling. Hair, nails, and mucosae were normal. There was no history of seizures, developmental delay, or sensory impairment, and systemic examination was unremarkable.

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Figure 1: (a) Bilaterally symmetrical verrucous papules and plaques arranged along Blaschko’s lines over the upper trunk. (b) Symmetrical, hyperpigmented verrucous lesions following Blaschko’s lines over the lower limbs. (c) Hyperkeratosis (black arrow), papillomatosis (red arrow) and acnathosis (blue arrow) Haematoxylin and eosin (H&E) stain, ×400 magnification

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Histopathology showed marked hyperkeratosis, acanthosis, and papillomatosis without epidermolysis, consistent with non-epidermolytic verrucous epidermal nevus (VEN) [Figure 1c]. VEN is a congenital hamartomatous proliferation of keratinocytes following Blaschko’s lines due to somatic mosaicism.^[1] Bilaterally symmetrical, extensive systematized involvement, sometimes resembling ichthyosis hystrix, is rare.^[2] Absence of epidermolysis and neonatal blistering helps differentiate it from epidermolytic variants associated with Keratin 1/keratin 10 (KRT1/KRT10) mutations.^[3] Although extensive lesions may be associated with epidermal nevus syndrome, no extracutaneous features were noted in this case.^[1] Management is mainly cosmetic, including topical keratolytics, retinoids, and laser therapies.^[1,2]