Background: Sotos syndrome is an autosomal dominant disease characterized by tall stature, advanced bone age, typical morphological abnormalities of the face and developmental delay. It is caused by mutations in the NSD1 gene located on chromosome 5. NSD1 mutations are detected in the majority of the Sotos patients, and include intragenic NSD1 mutations and microdeletions in the 5q35 region. Cardiovascular and urogenital symptoms are more frequent in the microdeletion group. Methods: Mutation analysis was performed in 4 patients with Sotos syndrome with typical phenotypic characteristics. Results: In each of the 4 patients a NSD1 mutation was found (2 frame shifts, 1 nonsense and 1 missense mutation). Two of our patients presented dysplastic kidneys with cysts and psychosis, respectively. Conclusions: We describe 4 Greek patients with Sotos syndrome. Apart from the typical phenotypic characteristics, 2 of our patients presented rare clinical manifestations such as dysplastic kidneys and psychosis. The 3 detected mutations are novel. Copyright (C) 2008 S. Karger AG, Basel