AbstractIntroductionThere is no well‐recognized biomarker for accurately predicting outcome in the presence of moyamoya disease (MMD), a progressive occlusive cerebrovascular disease of the internal carotid arteries or their branches. The aim of this study was to investigate the presence of endothelial progenitor cells (EPCs) and circulating endothelial cells (CECs) in MMD and correlate the findings with clinical features.MethodsPatients with MMD (n = 66) were compared with healthy controls (n = 81). Blood samples were obtained from an antecubital vein and analyzed using flow cytometry. EPCs were defined as CD31+CD45dimCD34brCD133+ and CECs as CD31brCD45−CD34dimCD133−. Univariate and multivariate linear regression analyses were carried out.ResultsThe CEC counts were significantly higher in the patients than in the controls (p = 0.008). In multivariate analysis, EPC counts were independently associated with age of patients with MMD (p = 0.049) and CEC counts were independently negatively associated with concomitant disease such as hypertension, diabetes mellitus, and coronary heart disease (p = 0.034).ConclusionsThis is the first study to investigate the presence of CECs in the plasma of patients with MMD, and the amount of CECs was negatively correlated with concomitant disease in these patients.