Somatic activating mutations of phosphatidylinositol 4,5-bisphosphate 3-kinase catalytic subunit alpha isoform (PIK3CA) and AKT serine/threonine kinase 1 (AKT1) have been detected in patients with PROS and Proteus syndromes, respectively (PIK3CAH1047R, PIK3CAE542K, PIK3CAE545K, PIK3CAG1049R and AKT1E17K). Here, PIK3CA is linked to Proteus syndrome.