This study is to find out the association between gut microbiota and moyamoya disease.

Moyamoya disease (MMD) is a rare cerebrovascular disorder, it is a major cause of stroke in children and young adults in Japan, Korea, and China, but its pathogenesis is not yet clear. Dysbiosis of gut microbiota may play a role in the pathological change of MMD. In this research, the investigators would perform metagenomic sequencing to find the characteristics of gut microbiota of MMD and to explore the correlations with metabolic, immune, and clinical symptoms. This research will not only help the understanding of the pathophysiology of MMD, but also may provide a reference for the selection of clinical treatment options.

Inclusion Criteria:

1. Diagnosis of MMD by DSA according to the Japanese guidelines published in 2012,
2. Stenosis or occlusion of the terminal internal carotid and the proximal middle and anterior cerebral arteries and unilateral or bilateral involvement
3. Age: 2-60 years old.

Exclusion Criteria:

1. Moyamoya syndrome,
2. Pregnancy,
3. Evidence of gastrointestinal infection/ inflammation/ obstruction
4. History of partial or total resection of small or large bowel, as well as gut reanastomosis,
5. Use of antibiotics within 2 weeks prior to symptoms onset,
6. Gastrointestinal malignancy
7. Any hospitalization within 3 months before recruitment

Consecutive patients diagnosed with MMD during hospitalization in Beijing Tiantan Hospital will be recruited. Eligibility will be determined through a checklist of inclusion and exclusion criteria. Control group will be recruited from medical out patient clinic.