Immunohistochemical differentiation between inflammatory linear verrucous epidermal nevus (ILVEN) and psoriasis

Inflammatory linear verrucous epidermal nevus (ILVEN) is a rare skin disorder with a clinical and histological resemblance to psoriasis. In the past clinical and histological criteria have been defined. However, there remains a discussion as to whether ILVEN is a disease entity distinct from linear psoriasis. Our objective was to compare by quantitative immunohistochemistry the subsets of T-lymphocytes and markers for epidermal growth and keratinisation in biopsies taken from skin lesions of 4 patients with psoriasis and 3 patients with ILVEN: 1. patients with psoriasis (case 1-4) 2. patient with ILVEN cum psoriasis (case 5) 3. patients with ILVEN sine psoriasis (case 6 and 7). Our aim was to delineate ILVEN from psoriasis. Four patients with active psoriasis and three patients with signs and symptoms of ILVEN are described in this case report. Two patients of the ILVEN group had only linear verrucous lesions (ILVEN sine psoriasis), and one patient had linear lesions combined with widespread psoriasis outside the linear verrucous lesion (ILVEN cum psoriasis). The following markers were investigated in skin biopsies taken from the aforementioned patients by quantitative immunohistochemistry: CD2, CD4, CD8, CD25, CD161, CD94, CD45RO, CD45RA, HLA-DR, Keratin-10, Ki-67. In patients with ILVEN (cum and sine psoriasis) the number of Ki-67 positive nuclei, tended to be lower, the number of keratin-10 positive cells and HLA-DR expression higher as compared to psoriasis. In ILVEN sine psoriasis all T-cell subsets and cells expressing NK receptors were reduced as compared to psoriasis, except for CD45RA+ cells, whereas in the patient with ILVEN cum psoriasis the number of these T cell subsets had an intermediary position. In particular the density of CD8+, CD45RO+ and CD2+, CD94 and CD161 showed a marked difference between ILVEN sine psoriasis and psoriasis. In addition to the increased keratin 10 expression in ILVEN sine psoriasis, T cells relevant in the pathogenesis of psoriasis are markedly reduced in ILVEN sine psoriasis as compared to psoriasis. T-cell subsets in ILVEN cum psoriasis had an intermediary position.