A Case of Naevoid Blaschkoid Psoriasis in a Two-Year-Old Child

Abstract

Psoriasis is a chronic, immune-mediated skin disorder characterised by well-demarcated erythematous plaque with micaceous scale. Naevoid Blaschkoid psoriasis is an unusual subtype that occurs along Blaschko lines. A two-year-old boy presented with erythematous scaly lesions distributed along the lines of Blaschko over the bilateral upper limb, the front of the chest, back, and the right lower limb. The lesions appeared four months ago and slowly progressed. There was no history of trauma, no skin lesions in other parts of the body, and no significant family history. Nail and mucosa were normal. Histopathology showed psoriasiform dermatitis with characteristics of psoriasis. The child was treated with topical clobetasol propionate 0.05% cream. Naevoid Blaschkoid psoriasis, in the absence of psoriatic lesion elsewhere on the body, is a rare manifestation. It has striking similarity with inflammatory linear verrucous epidermal nevus (ILVEN), both clinically and histologically. Naevoid psoriasis usually presents late, is asymptomatic or mildly pruritic, progresses rapidly, and responds favourably to antipsoriatic treatment. In contrast, ILVEN presents early, is intensely pruritic, slowly progressive, and is usually refractory to antipsoriatic treatment. Histologically, ILVEN demonstrates abruptly alternating areas of hypergranulosis with orthokeratosis, and parakeratosis with agranulosis. An inflammatory infiltrate is present in the upper dermis. Psoriasis presents with papillomatosis, acanthosis, and parakeratosis with absent or minimal granular layer. Immunohistochemical staining can be done in such doubtful cases. Involucrin would be detectable in psoriasis, but it is absent in ILVEN. Pathogenesis of linear psoriasis is unknown but might be explained by the concept of genetic mosaicism. Although rare, there have been a few reported cases of linear psoriasis occurring in early childhood.

Introduction

Psoriasis is a chronic, immune-mediated polygenic skin disorder. The characteristic lesions are localised or widespread and well-demarcated erythematous plaque with micaceous scale. Naevoid Blaschkoid psoriasis is an unusual subtype characterised by distribution of lesions along the Blaschko lines.[1]

The principal differential diagnosis to this entity is inflammatory linear verrucous epidermal nevus (ILVEN), which also occurs along the lines of Blaschko and is intensely pruritic and usually resistant to antipsoriatic treatment.

In contrast, linear psoriasis is often asymptomatic, or there may be mild pruritus. It tends to have a late manifestation and responds well to antipsoriatic treatment. However, there can be unusual naevoid distribution of psoriasis along the lines of Blaschko in early childhood on rare occasions.[2,3] In this article, we report an unusual case of naevoid psoriasis in a two-year-old child.

Case Report

A two-year-old boy presented to the dermatology outpatient department (OPD) with erythematous scaly lesions distributed along the lines of Blaschko over the bilateral upper limb, the front of the chest, back, and the posterior aspect of the right lower limb [Figures 1–3]. The lesions appeared four months ago and slowly progressed. There was no history of local trauma, no skin lesions in other parts of the body, and no family history of psoriasis or similar skin lesions. Nail and mucosa were normal.

Figure 1.

Blaschkoid lesions on the lower limb

Figure 3.

Lesions on the front of the chest

Figure 2.

Lesions in Blaschkoid pattern on the back

The major differential diagnosis was ILVEN, and skin biopsy was performed for further evaluation. The histopathology showed psoriasiform dermatitis with hyperkeratosis, parakeratosis, and thinning of the granular layer, characteristic of psoriasis [Figures 4 and 5]. The child was treated with topical clobetasol propionate 0.05% cream.

Figure 4.

10× view histopathology showing psoriasiform dermatitis

Figure 5.

40× view histopathology showing hyperkeratosis, parakeratosis, and thinned granular layer

Discussion

Naevoid Blaschkoid psoriasis, in the absence of psoriatic lesions elsewhere on the body, is a rare manifestation. There have been only a few cases reported in the literature so far. It has a striking similarity with ILVEN, both clinically and histologically, and hence remains a diagnostic challenge.[4,5]

The difference between the two has been discussed in literature. Naevoid psoriasis usually presents late, lesions are asymptomatic or mildly pruritic, and it progresses rapidly and responds favourably to antipsoriatic treatment. In contrast, an ILVEN lesion presents early, is intensely pruritic, slowly progressive, and usually refractory to antipsoriatic treatment.

Histologically, ILVEN demonstrates abruptly alternating areas of hypergranulosis with orthokeratosis, and parakeratosis with agranulosis. An inflammatory infiltrate is present in the upper dermis. Psoriasis presents with papillomatosis, acanthosis, and parakeratosis with absent or minimal granular layer. However, on many occasions, the clinical presentation and the histopathological features show a significant overlap between the two. Immunohistochemical staining can be done in such doubtful cases. Involucrin would be detectable in psoriasis, but it is absent in ILVEN.

Pathogenesis of linear psoriasis is unknown, but it could be explained by the concept of genetic mosaicism. The loss of heterozygosity can occur in somatic cells during embryogenesis, which results in homozygosity to one of the predisposing genes for psoriasis. Although rare, there have been a few reported cases of linear psoriasis occurring in early childhood.

Linear psoriasis should be considered as a distinct, separate entity that can be differentiated from ILVEN through careful history-taking, a through clinical examination, consistent histological findings, and favourable response to treatment. Immunohistochemistry, if available, can also be useful in doubtful cases.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patient understands that their name and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.