Verrucous epidermal naevus: a
misleading diagnosis for
Epidermal nevi (EN) are hamartomas of the skin that result
from mosaic postzygotic mutations.
There are several variants
of EN, the verrucous epidermal naevus (VEN) being the most
common. EN can be further subdivided into epidermolytic and
non-epidermolytic, important as in contrast with non-epider-
molytic EN, epidermolytic EN occurs sporadically (not herita-
ble), and it is not associated with extracutaneous abnormalities.
The epidermal naevus syndrome (ENS) is the association of EN
with abnormalities in other organ systems, mainly in the central
nervous system, skeletal system, eyes and oral cavity.
The aim of this paper was to report a case of a verrucous epi-
dermal naevus that affected the nail unit, and was treated as a
viral wart for 28 years.
A 28-year-old Caucasian female patient presented with a his-
tory of an asymptomatic verrucous plaque and nail dystrophy of
the right thumb since birth. Despite several treatments with
multiple therapeutic modalities mainly against viral warts,
including imiquimod cream, cryosurgery and keratolytics, there
was no change since then. She reported having had a skin biopsy
previously with the diagnosis of a viral wart. Close inspection
revealed a hyperkeratotic verrucous plaque involving the medial
aspect of the second metacarpus and the right thumb including
the proximal and lateral nail folds. The nail plate of the right
thumb showed longitudinal ridging, leukonychia and onycholy-
Histopathology was reported to us as having characteristics
suggestive of a viral wart. We re-evaluated the slides and
observed hyperkeratosis, papillomatosis, acanthosis with elonga-
tion of the rete ridges, and some vacuolization of keratinocytes
in the mid- and superﬁcial layers of the epidermis that had been
misinterpreted as koilocytes (
With the diagnosis of non-epidermolytic verrucous epidermal
naevus, we performed an examination of other systems, which
did not reveal any abnormality.
Verrucous epidermal naevus consists of hyperplasia of the
epidermis and is manifested as discrete, skin coloured to brown,
papillomatous papules or plaques, often linear or Blaschkoid in
They can be located anywhere, including the head, trunk
Patients with EN should be carefully evaluated for ENS,
including developmental problems, history of seizures, learning
disorders, or urinary tract symptoms and an extensive physical
Histopathology of VEN shows papillomatosis, hyperkeratosis,
acanthosis with elongation of the rete ridges, and sharp demar-
cation from the normal skin. Compact orthokeratosis is usually
seen in the stratum corneum. There are no suprapapillary thin-
ning of the epidermis, no columnar parakeratosis with included
microthrombi, no dilatation of the papillary capillaries, and no
cytopathic virus effects are seen allowing it to be distinguished
from viral warts.
‘Pseudo-koilocytes’ or vacuolated keratinocytes have been
and might be due to histopathological ﬁxation
artifacts, and in cases of lesions that present hyperkeratosis and
papillomatosis might be misinterpreted as viral wart, as in this
Differential diagnosis of periungual verrucous lesions that can
affect the nail plate includes viral warts, squamous cell carci-
noma, Bowen’s disease, congenital linear porokeratosis, epider-
molytic verrucous naevus, lichen striatus, inﬂammatory linear
verrucous epidermal naevus and linear psoriasis.
genesis of the nail dystrophy in this case is thought to reﬂect the
nail matrix involvement of VEN. To our knowledge, this is the
ﬁrst case in the literature of VEN associated with nail dystrophy.
This case highlights the importance for dermatologists and
physicians in general of taking a good clinical history and of
Figure 1 (a) Right hand, showing a hyperkeratotic verrucous pla-
que involving the medial aspect of the second metacarpus and the
right thumb; (b) Nail plate of the right thumb showing longitudinal
ridging, leukonychia and onycholysis.
Figure 2 Haematoxylin and eosin stain showing: (a) hyperkerato-
sis, papillomatosis, acanthosis with elongation of the rete ridges
(109); (b) vacuolization of keratinocytes in the mid- and superﬁcial
layers of the epidermis (1009).
© 2017 European Academy of Dermatology and Venereology
2018, 32, e86–e121
Letters to the Editor