毛毛樣腦血管病是腦部動脈血管原因不明的狹窄所造成的疾病，新形成的側枝循環在血管攝影下像一縷煙霧的影像為其特徵。文獻報導在患有毛毛樣腦血管病的病童以單側肢體無力、暫時性腦缺血發作、感覺異常及抽筋等為最常見的症狀。這裡我們報告一位十三歲男童一開始以舞蹈症表現的毛毛樣腦血管病。舞蹈症是一種不自主類似跳舞的動作，與許多疾病有關。臨床醫師在面臨兒童表現舞蹈症時，也必須把毛毛樣腦血管病列入鑑別診斷。腦部影像檢查以及血管攝影可以確定診斷，血管繞道手術。可以改善病童的舞蹈症

Moyamoya disease (MMD) is a chronic idiopathic cerebral vasculopathy primarily occurring in childhood and characterized by slowly progressive carotid artery narrowing and occlusion at the base of the brain. An extensive network of anastomoses forms (moyamoya vessels) between branches of the carotid arteries and appears as a “puff-of-smoke” pattern on an angiogram. Children with MMD may present with symptoms related to vascular insuffi ciency, such as transient ischemic attack, acute hemiplegia, seizures, paresthesia, etc. However, chorea is rarely noted in this disease. We herein report a 13-year-old boy with MMD in whom chorea was the initial presentation, and brain magnetic resonance cerebral angiography showed typical moyamoya vessels. His chorea dramatically improved after bypass surgery. We urge that when unusual involuntary movements, such as chorea, are noted in a child, brain imaging and angiography may guide clinical decision-making.