[Pentasomy X: a clinical case report].

Cytogenetic investigations gave evidence of pentasomy X in a 3-year-old female with typical facies and psychomotor retardation. The parents and the grandparents showed a normal karyotype. The clinical symptoms of our case were compared with the other authors, we found a low birth weight, short stature, delayed expressive language, multiple abnormalities of craniofacial skeleton and some minor deformities of the arts. The parental origin of the extra set of X chromosome were determined by the restriction fragment length analysis (RFLPs) using the very polymorphic probes M27beta, L1.28 and St14. These data support the hypothesis of a maternal meiotic double non-disjunction.