 While vascular anomalies are rare diseases, they can be life-threatening and devastating to affected children and their families. Advances in diagnosis, monitoring and therapies will be significantly improved if non-invasive biomarkers that are sensitive and specific can be identified. Identification of VEGF-D as a biomarker in LAM Lymphangiomyomatosis patients is an excellent example of how a blood biomarker can impact diagnosis and treatment. Biomarkers may also give insights into disease pathogenesis, as often they are released by cells that contribute to the disease process. The studies in this protocol will characterize and define biomarkers to aid in the diagnosis and treatment of patients with vascular anomalies. The differential diagnosis of some of these entities can be challenging, especially GLA versus KLA and KLA versus KHE. Obtaining a tissue biopsy to help in diagnosis can actually worsen the disease and so identification of specific blood biomarkers is highly desirable. Studies will measure angiogenic factors in serum and plasma samples at baseline and on therapy. 