This article reports the first case of Chinese girl diagnosed as Myhre Syndrome (MS) combined with Mayamoya disease (MMD). The symptomology of the patient is featured by sudden onset of right hemiplegia and seizure. Hemiplegia and seizure which are characteristics indicating existence of MMD, which led to prescription of DSA (Gold standard for MMD diagnosis) and an ultimate MMD diagnosis. The patient, also showed, beside right hemiplegia and seizure, mental retardation, typical facial dysmorphism, and additional inherited metabolic diseases were thus suspected and whole exome sequencing (WES) performed. A pathogenic variant (p.Ile500Thr) of SMAD4 gene was revealed by WES. From our knowledge based on PubMed search, this is the first case report showing the comorbidity of MMD and MS, featured by Myhre syndrome with late onset of right hemiplegia and seizure. Related literature review and hypothesized association of the two diseases are illustrated and discussed.