Brain AVM compactness score in children with hereditary hemorrhagic telangiectasia.

OBJECTIVE: The brain arteriovenous malformation (BAVM) nidus compactness score (CS), determined on angiography, predicts BAVM recurrence after surgical resection among children with sporadic BAVMs. We measured the angiographic CS for BAVMs among children with hereditary hemorrhagic telangiectasia (HHT) to determine CS characteristics in this population. METHODS: A pediatric interventional neuroradiologist reviewed angiograms to determine the CS of BAVMs in children with HHT recruited to the BVMC. CS is based on overall nidus and perinidal anomalous vessel compactness. CS categories included 1 = diffuse nidus, 2 = intermediate nidus, and 3 = compact nidus. RESULTS: Forty-eight of 78 children (61.5%) with HHT and brain vascular malformations had a conventional angiogram; 47 (97.9%) angiograms were available. Fifty-four BAVMs were identified in 40 of these 47 children (85.1%). Of 54 BAVMs in children with HHT, CS was 1 in 7 (13%), 2 in 29 (53.7%), and 3 in 18 BAVMs (33.3%) compared with CS of 1 in six (26.1%), 2 in 15 (65.2%), and 3 in 2 BAVMs (8.7%) among 23 previously reported children with sporadic BAVMs, p = 0.045 (Fisher's exact). Seven children with HHT had intracranial hemorrhage: 4 had CS = 3, 1 had CS = 2, and 2 had CS = 1. CONCLUSIONS: A range of CSs exists across HHT BAVMs, suggesting it may be an angiographic measure of interest for future studies of BAVM recurrence and hemorrhage risk. Children with HHT may have more compact niduses compared to children with sporadic BAVMs. Additional research should determine whether CS affects hemorrhage risk or post-surgical recurrence risk in HHT-associated BAVMs, which could be used to direct BAVM treatment.

Genetic testing in the evaluation of individuals with clinical diagnosis of atypical Sturge-Weber syndrome.

Sturge-Weber Syndrome (SWS) is a rare vascular malformation disorder characterized by abnormal blood vessels in the brain, skin, and eye. SWS is most commonly caused by a somatic mosaic GNAQ-p.Arg183Gln variant. In this series, 12 patients presented for clinical evaluation of SWS but were noted to have atypical features, and therefore germline and/or somatic genetic testing was performed. Atypical features included extensive capillary malformation on the body as well as the face, frontal bossing, macrocephaly, telangiectasia, overgrowth of extremities, absence of neurologic signs and symptoms, and family history of vascular malformations. Five patients had a somatic GNAQ or GNA11 pathogenic variant, one patient had a somatic mosaic likely-pathogenic variant in PIK3CA, and another one had a somatic mosaic deletion that disrupted PTPRD. The other five patients had germline variants in RASA1, EPHB4, or KIT. Our findings suggest that patients presenting for SWS evaluation who have atypical clinical characteristics may have pathogenic germline or somatic variants in genes other than GNAQ or GNA11. Broad germline and somatic genetic testing in these patients with atypical findings may have implications for medical care, prognosis, and trial eligibility.

Kaposiform lymphangiomatosis: Diagnosis, pathogenesis, and treatment.

Kaposiform lymphangiomatosis (KLA) is a life-threatening rare disease that can cause substantial morbidity, mortality, and social burdens for patients and their families. Diagnosis often occurs long after initial symptoms, and there are few centers in the world with the expertise to diagnose and care for patients with the disease. KLA is a lymphatic anomaly and significant advancements have been made in understanding its pathogenesis and etiology since its first description in 2014. This review provides multidisciplinary, comprehensive, and state-of-the-art information on KLA patient presentation, diagnostic imaging, pathology, organ involvement, genetics, and pathogenesis. Finally, we describe current therapeutic approaches, important areas for research, and challenges faced by patients and their families. Further insights into the pathogenesis of KLA may advance our understanding of other vascular anomalies given that similar signaling pathways may be involved.

Practice Variations in Managing Infantile Hemangiomas.

Infantile hemangioma (IH) is the most common benign tumor of infancy. For children with IH who require treatment, propranolol and other beta blockers have been shown to be safe and effective. Although consensus guidelines for managing IH have been published, anecdotal experience suggests that there remain variations in management. This study was performed to document these variations amongst providers and to identify areas for future research. We conducted an Internet-based survey of clinicians who treat patients with IH. Hypothetical cases and management scenarios were presented. Twenty-nine respondents participated in the survey. Most respondents use generic propranolol in infants with growing IH of the head and neck, with a goal dose of 2 mg/kg/d, until ~1 year of age. A variety of management strategies were documented including which patients should be treated, optimal dose and duration of therapy, how patients should be monitored, which patients should get additional workup, how propranolol should best be discontinued, and how often to see patients in follow-up. This study demonstrates wide practice variations in managing patients with IH. Further research is indicated to address these variations and develop additional/updated evidence-based guidelines.

How we approach genetics in the diagnosis and management of vascular anomalies.

Vascular anomalies are a heterogeneous group of disorders that are currently classified based on their clinical and histological characteristics. Over the past decade, there have been significant advances in molecular genetics that have led to identification of genetic alterations associated with vascular tumors, vascular malformations, and syndromes. Here, we describe known genetic alterations in vascular anomalies, discuss when and how to test, and examine how identification of causative genetic mutations provides for better management of these disorders through improved understanding of their pathogenesis and increasing use of targeted therapeutic agents in order to achieve better outcomes for our patients.

Neonatal vascular anomalies manifesting as soft-tissue masses.

The broad and heterogeneous spectrum of vascular anomalies ranges from an innocuous localized cutaneous discoloration to complex, extensive and life-threatening diagnoses. While many of these lesions are present at birth, smaller and deeper lesions might be clinically occult for months or years. Certain vascular anomalies commonly manifest in the prenatal or neonatal period and often have suggestive clinical and imaging features that can aid the radiologist in making a correct diagnosis. The characteristics of such lesions presenting very early in life, particularly those manifesting as soft-tissue masses, are the focus of this review.

Constitutively active PIK3CA mutations are expressed by lymphatic and vascular endothelial cells in capillary lymphatic venous malformation.

Capillary lymphatic venous malformations (CLVM) are complex vascular anomalies characterized by aberrant and enlarged lymphatic and blood vessels. CLVM appear during fetal development and enlarge after birth, causing life-long complications such as coagulopathy, pulmonary embolism, chronic pain, and disfigurement. Treatment includes surgical debulking, amputation, and recurrent sclerotherapy. Somatic, mosaic mutations in the 110-kD catalytic α-subunit of phosphoinositide-3-kinase (PIK3CA) gene have been previously identified in affected tissues from CLVM patients; however, the cell population harboring the mutation is still unknown. In this study, we hypothesized that endothelial cells (EC) carry the PIK3CA mutations and play a major role in the cellular origin of CLVM. We isolated EC from the lesions of seven patients with CLVM and identified PIK3CA hotspot mutations. The CLVM EC exhibited constitutive phosphorylation of the PI3K effector AKT as well as hyperproliferation and increased resistance to cell death compared to normal EC. Inhibitors of PIK3CA (BYL719) and AKT (ARQ092) attenuated the proliferation of CLVM EC in a dose-dependent manner. A xenograft model of CLVM was developed by injecting patient-derived EC into the flanks of immunocompromised mice. CLVM EC formed lesions with enlarged lymphatic and vascular channels, recapitulating the patient histology. EC subpopulations were further obtained by both immunomagnetic separation into lymphatic EC (LEC) and vascular EC (VEC) and generation of clonal populations. By sequencing these subpopulations, we determined that both LEC and VEC from the same patient express the PIK3CA mutation, exhibit increased AKT activation and can form lymphatic or vascular lesions in mouse.

Retrospective study of hematologic complications in patients with slow-flow vascular malformations undergoing sclerotherapy.

BACKGROUND: Slow-flow vascular malformations (SFVM) are associated with localized intravascular coagulopathy (LIC), which is characterized by elevated D-dimer and, when severe, hypofibrinogenemia. LIC results in intralesional clotting and hemorrhage and increases risk for significant thrombotic and bleeding complications. Sclerotherapy has been a suggested potential trigger for LIC worsening to disseminated intravascular coagulopathy. Hematologic complications of sclerotherapy in SFVM, along with low-molecular-weight heparin (LMWH) used to prevent worsening LIC, are largely unstudied. PROCEDURE: Medical records of patients with SFVM and LIC who underwent sclerotherapy at Cincinnati Children's Hospital Medical Center from July 2008 to December 2016 were reviewed for periprocedural hematologic complications. LMWH dose, frequency, and course length were evaluated. RESULTS: Fifty-nine patients with SFVM and LIC underwent 281 sclerotherapy procedures, of which 86% were in children. Eighty-five percent of patients received periprocedural LMWH, although at various doses and course lengths. No thrombotic complications occurred in children. One adult on LMWH developed pulmonary emboli after sclerotherapy. No major bleeding complications occurred postoperatively. In four patients, fibrinogen dropped below 100 mg/dL post-sclerotherapy, requiring cryoprecipitate. One patient required packed red blood cell (RBC) transfusion for sclerotherapy-induced hemolysis. No intraoperative bleeding or thrombotic events occurred. CONCLUSION: LMWH use, at subtherapeutic dosing, was common in this patient population and did not appear to increase risk of significant bleeding before, during, or after sclerotherapy. In children with SFVM, bleeding and thrombotic complications after sclerotherapy appear rare. Although safe, prospective studies are needed to evaluate the efficacy of LMWH to prevent worsening coagulopathy with procedures.

Sirolimus for the treatment of juvenile nasopharyngeal angiofibroma.

Juvenile nasopharyngeal angiofibroma (JNA) is a pathologically benign yet locally aggressive and destructive tumor that develops in the choana and nasopharynx. Historical treatment of JNA has included embolization, surgical resection, and radiation. Here, we describe three patients who received therapy with the mTOR inhibitor sirolimus with improvement in clinical symptoms, imaging, and overall well-being.

Single-stage embolization with n-butyl cyanoacrylate and surgical resection of venous malformations.

PURPOSE: Sclerotherapy or surgical resection is options for symptomatic venous malformations (VM). Sclerotherapy may require repetitive intervention and resection is often avoided due to operative morbidity. The purpose of this study was to report use of single-stage n-butyl cyanoacrylate glue embolization and surgical resection of focal VM. METHODS: A review of patients with focal VM who underwent glue embolization followed by resection at a single tertiary care vascular malformations center was performed. All embolizations were performed with ultrasound and fluoroscopy under the same anesthetic as resection. Patient characteristics and outcomes were evaluated. RESULTS: Fifteen procedures were performed in 12 patients with a total of 20 VM addressed, as several patients had multiple VM. Mean age was 16 ± 9 years. Malformation locations included scalp, hip, gluteal, labial, toe, finger, face, lip, chest, and foot and size ranged from 1.0 to 10.5 cm. Median (range) of prior sclerotherapy treatments was 3 (0-5) and three patients previously underwent surgical resection. Median blood loss was zero (0-10) mL. Surgical complications occurred after five procedures (33%) including superficial wound dehiscence and cellulitis. No complications required readmission or reoperation. At a median follow up of 195 (103-266) days, no patients have required additional treatment. CONCLUSION: Glue embolization and resection of focal VM of variable size and location appears to have durable results and low surgical morbidity. This single-stage procedure, often performed as an outpatient, may be utilized as upfront treatment for symptomatic malformations or for VM refractory to other treatments.

CT Angiography Findings of Pulmonary Arteriovenous Malformations in Children and Young Adults With Hereditary Hemorrhagic Telangiectasia.

OBJECTIVE. The purpose of this study was to evaluate the CT angiography (CTA) findings of pulmonary arteriovenous malformation (PAVMs) in patients with hereditary hemorrhagic telangiectasia and to correlate these findings with those of graded contrast-enhanced transthoracic echocardiography (CE-TTE). MATERIALS AND METHODS. A retrospective review was conducted of PAVMs visualized at CTA of patients with abnormal CE-TTE findings (3-point scale). Location, distribution, size, number, volume, grade, and relative attenuation (attenuation of PAVM divided by attenuation of aorta) of PAVMs were recorded. PAVMs were graded as follows on conventional and maximum-intensity-projection (MIP) images: 0, nodule, unlikely PAVM; 1, ground-glass opacity (GGO); 2, GGO with increased vascular network; 3, GGO or nodule with single vessel; 4, GGO or nodule with two or more vessels; 5, GGO or nodule with afferent and larger efferent vessels; 6, mature arteriovenous malformation. Correlation between PAVM grade and relative attenuation and between CTA variables and CE-TTE grades was assessed. RESULTS. Forty patients (median age, 14.9 years; range, 0.6-27.9 years) had 117 PAVMs at CTA: 107 peripheral, eight central, and two both peripheral and central. None of the PAVMs was diffuse. Median size and volume were 0.4 cm (range, 0.1-4.4 cm) and 0.031 mL (range, 0.0009-10.019 mL). At CTA, seven PAVMs were grade 1, five grade 2, 28 grade 3, 62 grade 4, two grade 5, and 13 grade 6. MIP images showed 39 of 117 PAVMs were higher grade. Statistically significant correlation was found between relative attenuation and PAVM grade (p < 0.001, r = 0.58) in 40 patients and between all CTA variables and CE-TTE (p < 0.05, strongest correlation with highest grades [p < 0.0001, r = 0.81]) in 32 patients. CONCLUSION. In children and young adults with hereditary hemorrhagic telangiectasia, grade 4 PAVMs were most common. Higher-grade PAVMs more often have right-to-left shunts.

Signaling pathways and inhibitors of cells from patients with kaposiform lymphangiomatosis.

BACKGROUND: Kaposiform lymphangiomatosis (KLA) is a rare lymphatic anomaly with significant morbidity and mortality. KLA is characterized by diffuse multifocal lesions comprised of focal areas of "kaposiform" spindled cells accompanying malformed lymphatic channels. The goal of this study was to identify activated signaling pathways in cells isolated from three KLA patients for the purpose of testing new therapies. PROCEDURE: Cells were obtained from the lungs of one patient isolated at autopsy and the spleen of two patients removed in surgery due to disease complications. A protein kinase array was performed on the KLA cell lysates and normal lymphatic endothelial cells. RESULTS: Higher activation of key signaling pathways in the KLA cells, including PRAS40, AKT1/2/3, and ERK-1/2, was identified by protein kinase array and confirmed by Western blot analysis. This indicated a role for highly activated PI3K-AKT and MAPK-ERK-1/2 signaling pathways in KLA cells. Cell proliferation studies assessed PI3K inhibitors (LY294002; BYL719), AKT inhibitor ARQ092, mTOR inhibitor rapamycin, and MAPK inhibitor U0126. These studies demonstrated that PI3K-AKT-mTOR and MAPK signaling are important mediators of KLA cell proliferation. BYL719 and rapamycin were more effective at inhibiting KLA cell proliferation than U0126. CONCLUSIONS: Our studies using cells from KLA patient lesions demonstrate that these cells are highly proliferative and the PI3K-AKT-mTOR and MAPK pathways are promising therapeutic targets. Development and clinical trials of PI3K, AKT, and MAPK inhibitors for cancer treatment and the data in this study lend support for early clinical trials assessing the efficacy of these inhibitors in KLA patients.

Efficacy of systemic sirolimus in the treatment of generalized lymphatic anomaly and Gorham-Stout disease.

BACKGROUND: Generalized lymphatic anomaly (GLA) and Gorham-Stout disease (GSD) are rare complicated lymphatic malformations that occur in multiple body sites and are associated with significant morbidity and mortality. Treatment options have been limited, and conventional medical therapies have been generally ineffective. Emerging data suggest a role for sirolimus as a treatment option for complex lymphatic anomalies. PROCEDURE: Disease response was evaluated by radiologic imaging, quality of life (QOL), and clinical status assessments in children and young adults with GLA and GSD from a multicenter systematic retrospective review of patients treated with oral sirolimus and the prospective phase 2 clinical trial assessing the efficacy and safety of sirolimus in complicated vascular anomalies (NCT00975819). Sirolimus dosing regimens and toxicities were also assessed. RESULTS: Eighteen children and young adults with GLA (n = 13) or GSD (n = 5) received oral sirolimus. Fifteen patients (83%) had improvement in one or more aspects of their disease (QOL 78%, clinical status 72%, imaging 28%). No patients with bone involvement had progression of bone disease, and the majority had symptom or functional improvement on sirolimus. Improvement of pleural and pericardial effusion(s) occurred in 72% and 50% of affected patients; no effusions worsened on treatment. CONCLUSIONS: Sirolimus appears effective at stabilizing or reducing signs/symptoms of disease in patients with GLA and GSD. Functional impairment and/or QOL improved in the majority of individuals with GLA and GSD with sirolimus treatment.

A xenograft model for venous malformation.

Vascular malformations are defects caused by the abnormal growth of the vasculature. Among them, venous malformation (VM) is an anomaly characterized by slow-flow vascular lesions with abnormally shaped veins, typically in sponge-like configuration. VMs can expand over years causing disfigurement, obstruction of vital structures, thrombosis, bleeding, and pain. Treatments have been very limited and primarily based on supportive care, compression garments, sclerotherapy, and/or surgical resection. Sirolimus treatment has recently shown efficacy in some patients with complicated vascular anomalies, including VMs. Activating somatic TIE2 gene mutations have been identified in up to 60% of VMs and PIK3CA mutations have been found in another 25%. Here, we report a xenograft model of VM that reflects the patients' mutation heterogeneity. First, we established a protocol to isolate and expand in culture endothelial cells (VM-EC) from VM tissue or VM blood of nine patients. In these cells, we identified somatic mutations of TIE2, PIK3CA, or a combination of both. Both TIE2 and PIK3CA mutations induced constitutive AKT activation, while TIE2 mutations also showed high MAPK-ERK signaling. Finally, VM-EC implanted into immune-deficient mice generated lesions with ectatic blood-filled channels with scarce smooth muscle cell coverage, similar to patients' VM. This VM xenograft model could be instrumental to test the therapeutic efficacy of Sirolimus in the presence of the different TIE2 or PIK3CA mutations or to test for efficacy of additional compounds in targeting the specific mutated protein(s), thus enabling development of personalized treatment options for VM patients.

Developmental pharmacokinetics of sirolimus: Implications for precision dosing in neonates and infants with complicated vascular anomalies.

BACKGROUND: Sirolimus has recently been shown to be efficacious and tolerable in pediatric patients with complicated vascular anomalies. Nevertheless, dosing information remains very limited especially for neonates and infants. The purpose of this study was to develop an age-appropriate sirolimus starting dosing regimen based on the developmental changes in drug elimination capacity using data collected in neonates and infants. PROCEDURE: A recently developed sirolimus maturation model [Emoto et al. CPT Pharmacometrics Syst Pharmacol, 2016] was used to simulate clearance estimates using realistic age and weight covariates for age cohorts aged 0-24 months. Next, predose concentrations at steady state were generated for each age cohort of neonates and infants. Dose requirements to attain predefined target trough concentration ranges (10-15 and 5-10 ng/ml) were simulated across the different age groups. Starting doses were chosen to maximize the likelihood of achieving sirolimus-targeted concentrations. RESULTS: The trajectory of simulated sirolimus clearances increased with age and was in agreement with the previous findings in the Phase 2 study. The proposed dosing regimens covered eight age cohorts and resulted in target attainment of more than 75-95% across selected regimens. CONCLUSIONS: This study identified age-appropriate sirolimus dosing regimens for neonates and infants. The algorithm in combination with therapeutic drug management will facilitate sirolimus precision dosing in young children with vascular anomalies. A prospective evaluation is being planned.

Response of Blue Rubber Bleb Nevus Syndrome to Sirolimus Treatment.

BACKGROUND: Blue rubber bleb nevus syndrome (BRBNS) is a rare multifocal venous malformation syndrome involving predominantly the skin and gastrointestinal tract. Traditional treatment modalities include corticosteroids, interferon-α, sclerotherapy, and aggressive surgical resection. Sirolimus has been used in several single case reports. PROCEDURE: We performed a single-institution retrospective review of four children with BRBNS, who received sirolimus as part of their treatment regimens. A diagnosis of BRBNS was based on clinical, radiologic, and pathologic criteria. RESULTS: Median age was 6.5 years (range: 2-16 years). Pathologic evaluations revealed a combined malformation with venous and lymphatic components. The novel finding of a lymphatic component was confirmed with PROX-1 immunostaining. Patients received oral sirolimus with target drug levels between 10 and 13 ng/ml. Responses to treatment were defined as stabilization/decrease in size of lesions; resolution of transfusion requirements; reduction in pain, and improvement in quality of life (QOL). Median time to response was 1.5 months (SD ± 0.96 month, range: 1-3 months). Median follow-up was 21 months (range: 18-26 months). Lesion size and characteristics improved in all patients. All patients reported decrease in pain and improvement in QOL. All three patients requiring transfusions became transfusion-independent. One patient had resolution of coagulopathy. Adverse effects of sirolimus consisted of mucositis in three patients and neutropenia in one patient. CONCLUSIONS: Sirolimus is safe and efficient for the treatment of BRBNS. Further prospective studies are needed to evaluate the long-term effectiveness of this drug. This is the first report that identifies a lymphatic component as part of BRBNS.

Capillary malformations.

Capillary malformation (CM), or port wine birthmark, is a cutaneous congenital vascular anomaly that occurs in 0.1%-2% of newborns. Patients with a CM localized on the forehead have an increased risk of developing a neurocutaneous disorder called encephalotrigeminal angiomatosis or Sturge-Weber syndrome (SWS), with complications including seizure, developmental delay, glaucoma, and vision loss. In 2013, a groundbreaking study revealed causative activating somatic mutations in the gene (GNAQ) encoding guanine nucleotide-binding protein Q subunit α (Gαq) in CM and SWS patient tissues. In this Review, we discuss the disease phenotype, the causative GNAQ mutations, and their cellular origin. We also present the endothelial Gαq-related signaling pathways, the current animal models to study CM and its complications, and future options for therapeutic treatment. Further work remains to fully elucidate the cellular and molecular mechanisms underlying the formation and maintenance of the abnormal vessels.

Current Practice: Rationale for Screening Children with Hereditary Hemorrhagic Telangiectasia for Brain Vascular Malformations.

BACKGROUND: Hereditary hemorrhagic telangiectasia is an autosomal dominant vascular dysplasia characterized by mucocutaneous telangiectasias, recurrent epistaxis, and organ vascular malformations including in the brain, which occur in about 10% of patients. These brain vascular malformations include high-flow AVMs and AVFs as well as low-flow capillary malformations. High-flow lesions can rupture, causing neurologic morbidity and mortality. STATE OF PRACTICE: International guidelines for the diagnosis and management of hereditary hemorrhagic telangiectasia recommend screening children for brain vascular malformations with contrast enhanced MR imaging at hereditary hemorrhagic telangiectasia diagnosis. Screening has not been uniformly adopted by some practitioners who contend that screening is not justified. Arguments against screening include application of short-term data from the adult A Randomized Trial of Unruptured Brain Arteriovenous Malformations (ARUBA) trial of unruptured sporadic brain AVMs to children with hereditary hemorrhagic telangiectasia as well as concerns about administration of sedation or IV contrast and causing patients or families increased anxiety. ANALYSIS: In this article, a multidisciplinary group of experts on hereditary hemorrhagic telangiectasia reviewed data that support screening guidelines and counter arguments against screening. Children with hereditary hemorrhagic telangiectasia have a preponderance of high-flow lesions including AVFs, which have the highest rupture risk. The rupture risk among children is estimated at about 0.7% per lesion per year and is additive across lesions and during a lifetime. ARUBA, an adult clinical trial of expectant medical management versus treatment of unruptured brain AVMs, favored medical management at 5 years but is not applicable to pediatric patients with hereditary hemorrhagic telangiectasia given the life expectancy of a child. Additionally, interventional, radiosurgical, and surgical techniques have improved with time. Experienced neurovascular experts can prospectively determine the best treatment for each child on the basis of local resources. The "watch and wait" approach to imaging means that children with brain vascular malformations will not be identified until a potentially life-threatening and deficit-producing intracerebral hemorrhage occurs. This expert group does not deem this to be an acceptable trade-off.

Barriers to Genetic Testing in Vascular Malformations.

Importance: Vascular malformations (VMs) are rare disorders of vasculogenesis associated with substantial morbidity. Improved understanding of their genetic basis is increasingly guiding management, but logistical barriers to obtaining genetic testing in patients with VM may constrain treatment options. Objectives: To examine the institutional mechanisms for and obstacles to obtaining genetic testing for VM. Design, Setting, and Participants: This survey study invited members of the Pediatric Hematology-Oncology Vascular Anomalies Interest Group, representing 81 vascular anomaly centers (VACs) serving individuals up to 18 years of age, to complete an electronic survey. Respondents were mostly pediatric hematologists-oncologists (PHOs) but included geneticists, genetic counselors, clinic administrators, and nurse practitioners. Responses that were received between March 1 and September 30, 2022, were analyzed with descriptive methods. Requirements for genetic testing by several genetics laboratories were also reviewed. Results were stratified by size of the VAC. Main Outcomes and Measures: Vascular anomaly center and associated clinician characteristics and practice patterns for ordering and obtaining insurance approval for genetic testing for VMs were collected. Results: Responses were received from 55 of 81 clinicians, for a response rate of 67.9%. Most respondents were PHOs (50 [90.9%]). Most respondents (32 of 55 respondents [58.2%]) replied that they order genetic testing on 5 to 50 patients per year and reported a genetic testing volume increase of 2- to 10-fold over the past 3 years (38 of 53 respondents [71.7%]). Most testing was ordered by PHOs (35 of 53 respondents [66.0%]), followed by geneticists (28 [52.8%]) and genetic counselors (24 [45.3%]). In-house clinical testing was more common at large and medium-sized VACs. Small VACs were more likely to use oncology-based platforms, which potentially miss low-frequency allelic variants in VM. Logistics and barriers varied by size of the VAC. Obtaining prior authorization was the duty shared among PHOs, nurses, and administrative staff, but the burden of insurance denials and appeals were on PHOs (35 of 53 respondents [66.0%]). Lack of administrative support; unclear institutional, insurance, and laboratory requirements; and lack of clinician education were barriers to genetic testing at VACs of all sizes. The effort to obtain genetic testing for patients with VM, compared with patients with cancer, was perceived as excessive, despite genetic testing being considered standard of care for this population. Conclusions and Relevance: Results of this survey study showed the barriers to genetic testing for VM across VACs, described differences between VACs based on size, and proposed multiple interventions to support clinicians ordering genetic testing for VM. The results and recommendations should have broader application to clinicians caring for patients for whom molecular diagnosis is important to medical management.