Skeletal abnormalities of the upper limbs - Neonatal diagnosis of 49,XXXXY syndrome

► A case of neonatal diagnosis of 49,XXXXY syndrome is presented. ► Identification was prompted by a bilateral thickening of the radioulnar joints. ► In contrast to previous reports, radioulnar synostosis was present at birth. ► Microsatellite analysis showed two diverse X chromosomes, each present in two copies.