Genetic and Phenotypic Features of 2 Northern Italy Families with Dowling-Degos Disease Type 4.

Dowling-Degos disease (DDD) is an autosomal dominant genodermatosis involving the folds with lentiginous hyperpigmentation and reddish-brown papules. Four main types of DDD with variable clinical presentations likely related to the heterogeneity of the gene variant landscape have been implicated. Pathogenic keratin 5 gene gene variants favor a reticular distribution with predominant fold involvement, whereas pathogenic variants in lead to a widespread form with acantholytic features previously named Galli-Galli disease, now belonging to the disease spectrum of DDD and renamed DDD type 4. This study details the clinical and histopathological features associated with the sequence variant c.205C>T, p.(Arg69∗) in of 2 families from northern Italy affected by DDD4. Despite sharing the same variant, clinical manifestations varied among the affected members of the 2 families. Environmental factors probably contributed to phenotypic variability and symptoms exacerbation. Histopathology was sustained by digitiform rete ridges, suprabasal acantholysis, and dyskeratosis. Moreover, we detected aberrant keratin 5 gene expression in 2 biopsies. A review of the literature on -related DDD subtypes contextualizes these findings. The fact that several patients have been reported to carry the variant c.205C>T, p.(Arg69∗) might point to a potential mutational hotspot.