Abstract:  Objective To explore the clinical features and the gene mutations in MECP2 duplication syndrome. Methods The clinical data of a child with developmental retardation and hypophrenia accompanied with respiratory tract infection was analyzed retrospectively. Microarray analysis technique was used to detect the genes in the patient and his family. The pertinent literature was reviewed. Results A 1-year and 7-month old boy was found to have hypotonia, developmental delay, and recurrent respiratory tract infections after birth. Microarray analysis showed a duplication of 441.88kb in Xq28 area and diagnosis of MECP2 duplication syndrome was confirmed. His grandmother, mother, and two aunts were found duplication of 441.73-441.88kb in Xq28 area, all of whom were MECP2’s female carrier. Conclusions The improvement of chromosome chip technology inspection is helpful to the early diagnosis of MECP2 duplication syndrome.