Both the new classification proposal [56] and the Consensus Statement agree that the 3 major criteria are resistance to PTH (rPTH), ectopic ossifications (EO) and brachydactyly (BR), that maybe variably combined in a given patient and associated with other supporting signs and symptoms such as growth impairment (either intrauterine or post-natal), specific face characteristics, obesity, additional hormone resistances, cognitive impairment, mineralization defects such as enamel hypoplasia, delayed tooth eruption or tooth ankylosis, oligodontia or hypodontia, advanced skeletal maturation. This evidence concerns the gene PTH and brachydactyly.