The first meeting of the RHU COSY project was held at Institut Necker – Enfants Malades (INEM) on December 10th 2019 and brought together member of the consortium for a first presentation of the project. RHU COSY gathers together 11 partners and 1 patient association, combining all the necessary skills to propose innovative tools in physiopathology, genetics, imaging, and care reorganization. Our goal is to re-define medical care and offer a unique multidisciplinary service dedicated to patients with Overgrowth Syndromes (OS).