In current practice, options for venous and lymphatic malformations remain limited. Recently an oral medication, sirolimus, has been found to benefit patients when taken once or twice a day for several months. Unfortunately there are many side effects associated with this medication, some of which can be severe including, neutropenia, oral ulcerations, and lab abnormalities. The purpose of this study is to determine if once weekly dosed sirolimus will be effective for the treatment of venous and lymphatic malformations. Additionally, the study will evaluate patient satisfaction and identify adverse effects. Participants will be on the medication for 6 months with an option to continue after this time period.

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.