We found that HHT patients with BAVM had lower levels of GP130 (PI = 0.78, 95% CI 0.68 to 0.89, p < 0.001, q = 0.017), soluble vascular endothelial growth factor receptor 3 (sVEGFR3) (PI = 0.75, 95% CI 0.63 to 0.88, p = 0.001, q = 0.017), soluble intracellular adhesion molecule 1 (sICAM1) (PI = 0.74, 95% CI 0.62 to 0.88, p = 0.001, q = 0.017), and TSP2 (PI = 0.59, 95% CI 0.44 to 0.80, p = 0.001, q = 0.017) compared to HHT patients without BAVM. This evidence concerns the gene FLT4 and arteriovenous malformations of the brain.