Moyamoya disease (MMD) is a rare and progressive cerebrovascular disorder characterized by the gradual stenosis (narrowing) and occlusion of critical intracranial arteries. The etiology of this disease is still unknown. Here we use Laser capture microdissection followed by shotgun proteomics to analyse the brain of a moyamoya patient. We found that phenotypic switching of VSMCs may be involved in the occlusion of the arteries. In addition, invasion of immune cells such as macrophages, in the occluding tissue were found, strengthening the hypothesis that an abberant immune response to infection may be one of the key mechanisms in MMD pathology.