Use of angiopoietin-2 as a biomarker in vascular anomalies beyond complex lymphatic anomalies

Abstract Introduction: The study of vascular anomalies (VA) is a rapidly evolving field with the recent discovery of somatic lesional mutations in oncogenes suspected to be the drivers of these diseases. Although cancer therapeutics are currently being repurposed for these pathologies, definitive diagnosis and treatment monitoring remain challenging in patients with VA. We have previously described the use of serum angiopoietin-2 (Ang-2) levels as a diagnostic and therapy monitoring biomarker in Kaposiform Hemangioendothelioma (KHE) and Kaposiform Lymphangiomatosis (KLA). Kasabach-Merritt phenomenon (KMP) or KMP-like coagulopathy, characterized by severe thrombocytopenia and hypofibrinogenemia, can be a prominent feature of KHE and KLA. We have previously observed significantly elevated Ang-2 (>/=10,000pg/mL) in the serum of patients with KLA and KHE with KMP that improves with treatment and corresponds to improving coagulopathy. However, it is unclear whether Ang-2 is elevated or clinically significant in other complex lymphatic anomalies (CLA) and VA, especially the ones with underlying coagulopathy. Aim: In this single-center retrospective data review, we sought to investigate the use of Ang-2 as a serum biomarker for other CLA including Gorham Stout Disease (GSD) and Generalized Lymphatic Anomaly (GLA) and assess its clinical relevance in high-morbidity VA including capillary-lymphatic venous malformations (CLVM) with or without overgrowth, lymphatic malformations (LM), and venous malformations (VM). Methods: We retrospectively reviewed serum Ang-2 levels in patients with VA evaluated at our institution between August 2020 and June 2025. Ang-2 was measured using a CLIA-certified assay available exclusively at our institution (normal range of 1434-4141 pg/mL). Diagnosis, treatment data, and coagulation markers (D-dimer and fibrinogen) were also collected. This study was approved by the IRB at Cincinnati Children's Hospital Medical Center. Results: Among 30 patients with VA (4 GLA, 3 GSD, 9 CLVM with and without overgrowth, 8 extensive VM, 6 isolated LM), 46 serum Ang-2 measurements were obtained. At first Ang-2 measurement, 8 patients (3 GLA, 3 CLVM, 1 VM, 1 LM) were on disease-modifying therapies (DMT), including sirolimus or alpelisib. Most patients with VM (6/8, 75%) had D-dimer levels > 2 times the upper limit of normal (>2x ULN) without elevated Ang-2. Mildly elevated Ang-2 (4141 – 9999 pg/mL) was observed in 1 patient with GLA (on DMT) and 1 patient with GSD (not on DMT). Two patients with CLVM had elevated Ang-2 levels; one (on DMT) had an Ang-2 of 11,000 pg/mL but had sepsis and necrotizing enterocolitis at time of collection. The other patient with CLVM was not on DMT. Two LM patients had mildly elevated Ang-2; none were on DMT. One patient with LM had elevated Ang-2 (slightly above 10,000 pg/ml) with active skin ulceration. Overall, 21/30 (70%) patients had elevated D-dimer, with > 2x ULN in 12/30 (40%). No correlation was found between D-dimer and Ang-2 levels (r2 <0.01). Discussion:This study supports the utility of Ang-2 as a serum biomarker in VA. A previously proposed serum Ang-2 cut-off of 10,000 pg/mL to distinguish KLA and KHE with KMP from other VA is reinforced by our findings, as no other VA showed persistently elevated Ang-2 in the absence of other confounding factors. Serum Ang-2 levels were elevated in the context of infection and inflammation, consistent with its known role as an inflammatory marker. Notably, serum Ang-2 levels were not elevated in VM, even with markedly elevated D-dimer, suggesting distinct coagulopathy mechanisms. Thus, when interpreted within clinical context, Ang-2 remains a valuable biomarker for differentiating KLA and KHE with KMP from other VA. Limitations include small sample size and measurement during DMT in some cases. Further studies are needed to better understand the mechanisms driving Ang-2 elevations in these diseases.