The leading clinical small molecule PI3K p110α inhibitor is BYL719 (tradename alpelisib by Novartis), which was approved by the FDA in 2019 for the treatment of PIK3CA-mutated advanced or metastatic breast cancer in combination with fulvestrant, and is also a promising therapy for patients with PIK3CA-related overgrowth syndrome [6]. This evidence concerns the gene PIK3CA and overgrowth syndrome.