[X tetrasomy (48,XXXX karyotype) in a girl with altered behavior]. / Tetrasomía X (cariotipo 48,XXXX) en una niña con trastorno de conducta.

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.