[X tetrasomy (48,XXXX karyotype) in a girl with altered behavior].

INTRODUCTION We report the case of a 14-year-old girl with mental retardation and dysmorphic features referred to child psychiatry because of altered behavior at school. MATERIAL AND METHODS Karyotyping (GTG banding), in situ fluorescent hybridization (FISH) and molecular study of parental origin by polymorphic STS were performed. RESULTS Genetic study revealed a 48,XXXX karyotype with a maternal origin of the X-tetrasomy. The mechanism was successive non-dysjunction at meiosis I and II. CONCLUSIONS The interest of this case lies in the rarity of the chromosomal anomaly and its late diagnosis, leading to a failure to adapt the girl's education to her needs, with consequences for her psyche.