Overgrowth syndromes are rare genetic disorders defined by tissue hypertrophy that can be either localized or generalized, affecting both latitudinal and longitudinal growth. The genes involved in overgrowth syndromes are not well characterized but mostly concern the PIK3CA/AKT/mTOR pathway, a major actor of cell growth and proliferation. The mutations are not inherited but occurs during embryogenesis leading to somatic mosaicism. Owing to the variability of the clinical presentation, their exact prevalence is yet unknown. In order to answer this question, the investigators team create here the first French national registry on overgrowth syndromes.