24VA022; VATCH Alpelisib for TIE2/PIK3CA Pathway VAs

The study will enroll participants 2 months of age up to 30 years of age. The purpose of this study is to assess the effectiveness and safety of Alpelisib (the "Study Drug") in patients with PIK3CA/TIE-2/TEK pathway driven vascular anomalies (VA). Alpelisib has been approved by the U.S. Food and Drug Administration (FDA) for treating adults and children with certain types of breast cancer. Its use in this study is considered experimental because FDA has not approved the study drug for treating people with VAs. Study participation will last for up to 3 years and will involve regular study visits to Children's Hospital of Philadelphia (CHOP)'s Philadelphia Campus. Participants will need to take the study drug Alpelisib for at least 2 years, or up to 3 years in total if there is a positive response. Participating in this research means you will attend up to 16 clinic visits for the purposes of the study. Most visits will take approximately 30 minutes, but some visits will take approximately 2 hours, because you will be asked to complete questionnaires about your experience. Participating in this research also means taking the study drug, having pictures taken, and completing study drug diaries. There is also an optional portion to this study that involves collecting blood for biomarker testing.