49,XXXXY Syndrome with Diabetes Mellitus

49,XXXXY syndrome is a rare sex chromosome aneuploidy and characterized by mental retardation, skeletal defects, craniofacial anomalies and hypogonadism. The increased frequency of diabetes mellitus in patients with Klinefelter syndrome and other types of X-chromosome polysomy has been reported, but no cases of diabetes mellitus in adult with 49,XXXXY syndrome have been reported so far. We report an 18-year-old patient with 49,XXXXY syndrome accompanying diabetes mellitus.