RESUMEN
Smith-Magenis syndrome [SMS] is a multisystem, neurodevelopmental genetic disorder associated with mental retardation that predisposes individuals to a distinct pattern of maladaptive behaviors and other neuropsychological impairments. A family with a mental retarded male individual suspected of this syndrome were referred to our center for prenatal diagnosis. After genetic counseling, karyotyping was performed for confirmation of the disease. The results indicated that both parents were normal and the affected child had del[17][p11.2 [right arrow]p12]. The chromosomal anomaly with facial characteristics not particularly evident, mental retardation, behavioral troubles, hyperactivity, autistic traits and dysarticulation led to the diagnosis of the Smith-Magenis syndrome