IntroductionMethyl CpG binding protein 2 (MECP2) (OMIM *300005) is located at Xq28 and is a multifunctional gene with ubiquitous expression. MeCP2 have many function include orchestrate chromatin compartmentalization and higher order genome architecture[1]. MeCP2 is necessary for normal neuronal function and overall health throughout the lifespan[1]. Mutations in MECP2 can generate a wide spectrum of clinical presentations that range from mild intellectual impairment to severe neonatal encephalopathy and premature death[2]. Female mice deficient became hypoactive and exhibited motor and breathing defects after 3 months of age[3]. MeCP2 is a DNA binding protein which involved in higher order chromatin organization, RNA splicing, mutations in Mecp2 affect virtually all organs and tissues[2]，also include metabolic anomalies, including reduced N-acetylaspartate, myo-inositol, glutamine plus glutamate[4], cholesterol metabolism[5], liver lipid metabolism[6], Tyrosine metabolism[7] ,Platelet activation and espiratory metabolism[8]. But the molecular functions of MeCP2 human remain unclear in human. In order to find more Molecular functions in human of MeCP2 variant，the serum proteome of MeCP2 p.Lys254* variant patient was analyzed by TMT-labeled quantitative proteomics. Interesting consistent with null mutation mice Platelet activation，Tyrosine metabolism, Fatty acid degradation and metabolism related proteins were changed significantly[7, 9]. Beside this we found carbon metabolism, arginine biosynthesis, glycolysis were changed significant. Our discovery of a new spontaneous MeCP2 nonsense mutation and enriches the knowledge of Rett syndrome and provides a reference for the early diagnosis and treatment of Rett syndrome