Abstract
Porokeratosis is a rare disease of epidermal keratinization characterized by the histopathological feature of the cornoid lamella, a column of tightly fitted parakeratocytic cells, whose etiology is still unclear. Porokeratosis of Mibelli is a subtype of porokeratosis presenting a single plaque or a small number of plaques of variable size located unilaterally on limbs. It frequently appears in childhood and occurs with a higher incidence in males. Cytogenetic analyses were performed in all members of the family on lesioned and uninvolved skin. An array-CGH analysis was also performed utilizing the Human Genome CGH Microarray Kit G3 400 with 5.3 KB overall median probe spacing. Gene expression was performed on skin fibroblasts. In this study, we describe a Caucasian healthy 4-year-old child and his father showing features of porokeratosis of Mibelli. Array-CGH analysis revealed an interstitial 429.5 Kb duplication of chromosome 18p11.32-p11.3 containing four genes, namely: SMCHD1, EMILIN2, LPIN2, and MYOM1 both in patient and his father. EMILIN2 resulted overexpressed on skin fibroblasts. Also other members of this family, without evident signs of porokeratosis, carried the same duplication. Among these genes, we focused our attention on elastin microfibril interfacer 2 (EMILIN2) gene. Apoptosis plays a fundamental role in maintaining epidermal homeostasis, balancing keratinocytes proliferation, and forming the stratum corneum. EMILIN2 is known to trigger the apoptosis of different cell lines negatively affecting cell survival. It is expressed in the skin. We could speculate that the duplication and overexpression of EMILIN2 cause an abnormal apoptosis of epidermal keratinocytes and alter the process of keratinization, even if other epigenetic and genetic factors could also be involved. Our results could contribute to a better understanding of the pathogenesis of porokeratosis of Mibelli.
Highlights
Porokeratosis (PK) is a heterogeneous group of disorders of epidermal keratinization characterized by atrophic patches surrounded by a stack of tightly fitted parakeratotic cells called the cornoid lamella, which is the histopathological feature for this group of disorders
Porokeratosis of Mibelli (PM) and disseminated superficial porokeratosis (DSP) are clinical variants that appear in childhood
Our patients were diagnosed with porokeratosis of Mibelli on the basis of the number, size and distribution of plaques, as well as age of onset
Summary
Porokeratosis (PK) is a heterogeneous group of disorders of epidermal keratinization characterized by atrophic patches surrounded by a stack of tightly fitted parakeratotic cells called the cornoid lamella, which is the histopathological feature for this group of disorders. We describe a young male and his father showing features of porokeratosis of Mibelli and a 429 Kb interstitial duplication of chromosome 18p11.32-p11.31. Annular plaques presented with central atrophy and elevated keratotic borders that had a longitudinal furrow, with slightly raised whitish-red portions on either side of the furrow (Fig. 1, A, B). C) The patient’s skin biopsy shows slight papillomatosis and ortokeratosis of epidermis and a cornoid lamella; the derma appears normal (H&E, 106). E) The examination of the skin biopsy of the father shows atrophic epidermis with two cornoid lamellae; solar elastosis and sparse perivascular lymphocytic infiltrate can be recognized (H&E, 106). The median gene expression of EMILIN2 and LPIN2 in patient’s fibroblast was 1.79 and 1.62-fold higher than in normal fibroblasts, respectively
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