Weekly Sirolimus Therapy

Inclusion Criteria: * Patient 2 years of age and older * Venous, lymphatic, or venolymphatic malformations Exclusion Criteria: * Children with contraindication to use of sirolimus * Children with history of transplant * Children with a history of natural immunodeficiency * Children with a history of artificially induced immunodeficiency * Children with a history of a serious or life-threatening infection * Children taking CYP3A4 inhibiting medications * Children taking strong CYP3A4 inducers to avoid subtherapeutic dosing/exposure. * Inability or unwillingness of subject or legal guardian/representative to give informed consent * Women that are or may become pregnant o Sirolimus is a Pregnancy Category C drug. No randomized controlled studies have been done on pregnant women. Women of childbearing potential must be on effective contraception prior to, during, and for 12 weeks following sirolimus therapy.