Linear psoriasis or ILVEN? A pediatric case unraveling the mosaic puzzle.

Linear psoriasiform eruptions in children are diagnostically challenging, particularly when they follow Blaschko's lines. The main differential diagnosis includes inflammatory linear verrucous epidermal nevus (ILVEN) and linear psoriasis (LP), a rare mosaic variant. We describe the case of a 5-year-old boy with extensive unilateral lesions clinically suggestive of both entities. Histology revealed Munro microabscesses and psoriasiform hyperplasia. The patient showed rapid improvement with topical calcipotriol/betamethasone, followed by long-term remission. Notably, after 8 years of follow-up, the lesions remained strictly confined to the original Blaschkoid distribution, with no extracutaneous involvement and only mild recurrences. This clinical course strongly supports the diagnosis of isolated linear psoriasis (type 1 mosaicism). Few pediatric cases in the literature have documented such a long and stable evolution, making this report a valuable contribution to the distinction between LP and ILVEN. The case highlights the importance of integrating clinical, histological, and longitudinal data when evaluating linear dermatoses in children.