ARTICLE
Auteur(s) : Norberto López1,
Blanca Cabra2, Rosa Castillo1, Inmaculada
Alcaraz1, Ricardo Bosch1, Enrique
Herrera1
1Department of Dermatology, University Hospital.
School of Medicine. 29010 Málaga, Spain
2Department of pathology, University Hospital. School of
Medicine. 29010 Málaga, Spain
accepté le 26 Mars 2008
A 21-year-old woman presented at our department with a 3-month
history of asymptomatic linear erythematous, scaly lesions over the
left leg. Cutaneous examination showed well-defined, irregularly
shaped erythematous scaly papules and plaques, arranged in a linear
pattern extending from the external malleolus to just below the
left buttock. On the posterior side of the thigh they assumed the
typical band-like pattern following Blaschko’s lines (figure 1). The nails and
mucosa were not involved. There was no history of trauma to the leg
prior to the appearance of the linear lesion, nor did the patient
complain of any pain or burning before its onset. No family history
of similar eruptions was found and the patient was otherwise in
good health. A skin biopsy taken from a thigh lesion showed typical
features of psoriasis, including acanthosis with regular elongation
of the rete ridges, parakeratosis, hypogranulosis and thinning of
the suprapapillary epidermis with spongiform pustules. Dermal
papillae showed edema and dilated tortuous vessels. Subsequently,
the woman was given the diagnosis of blaschkolinear psoriasis.
Topical treatment with calcipotriol/Betametasona almost completely
cleared it up, except for some remaining slightly hypopigmented
patches.
Discussion
Lesions distributed along Blaschko’s lines may occur in patients
with psoriasis as a part of Koebner’s phenomenon [1]. However, true
linear psoriasis in the absence of lesions elsewhere is extremely
rare. Happle proposed to distinguish between linear psoriasis of
the superimposed type, in which a pronounced linear involvement is
associated with psoriasis vulgaris, and linear psoriasis of the
isolated type, in which disseminated lesions of psoriasis are
constantly absent [2]. In that context, considerable diagnostic
confusion exists, since, clinically, these lesions can very closely
resemble other linear dermatoses such as inflammatory linear
verrucous epidermal nevus (ILVEN) and lichen striatus (LS).
Although these 3 entities may present in a similar manner, specific
clinical and histopathology features help to distinguish them, and
it is important for the clinician to be able to differentiate among
them. ILVEN is a distinct variety of keratinocytic epidermal naevus
that is clinically inflammatory and is usually psoriasiform [3].
Histologically, ILVEN classically demonstrates hypergranulosis and
parakeratosis alternating with hypogranulosis and orthokeratosis
[4]. Characteristically, it tends to be unresponsive to the
classical methods of antipsoriatic treatment [5]. LS is a
papulosquamous disorder with a distinctive linear distribution
corresponding in many cases to the pattern of Blaschko lines [6].
The histopathological features of LS are non-specific but the main
pathological changes consist of a lymphocytic infiltrate mainly
centered around the subpapillary vessels, extending into some of
the dermal papillae and aligned along the sweat glands and hair
follicles [7]. To our knowledge, the lesions present in our case
are not of the ILVEN or LS type because the eruption was
asymptomatic, the typical histological features were absent and
improvement with anti-psoriatic treatment was observed. Furthermore
epidermal naevi that have been “invaded” by psoriasis, as a
manifestation of the isomorphic response, have been reported [8].
Our patient developed psoriatic lesions without any sign of a
preceding lesion, which disallows the invasion of a linear
epidermal nevus by psoriasis. Less common psoriasis that presents
in a blaschkolinear pattern may have an early onset. The term
congenital Blaschkoid or nevoid psoriasis was suggested for these
lesions [9-11]. However the existence of a congenital Blaschkoid
psoriasis form has rarely been reported, and some authors believe
that these are cases of inflammatory linear verrucous epidermal
naevus [12]. Several theories have been proposed as to the
pathogenesis of blaschkolinear psoriasis, but most authors believe
that it may originate from early loss of heterozygosity or from any
other mutation occurring at one of the many gene loci involved in
psoriasis [13]. Moss argued that such patients are mosaic for an
epidermal “susceptibility gene” responsive to generalized
immunological factors [14].
In conclusion, we consider that the present case exhibits all
the features of psoriasis supporting the existence of a truly
blaschkolinear psoriasis.
Acknowledgements
Financial support: none. Conflict of interest: none.
References
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