Studies of 5 isolated ECFCs from patients with the low VWF phenotype show several abnormalities of VWF expression, storage, and release. Of particular note, scRNA-seq demonstrated reduced VWF mRNA levels in 4 of 5 patients, and a different pattern of gene expression was seen in low VWF vs control ECFCs. HUVECs, Human umbilical vein endothelial cells; KD, knock down.