Fragile X mental retardation: prevalence in a group of institutionalized patients in Italy and description of a novel EEG pattern.

We have studied the prevalence of the fra (X) and of the autosomal fragile sites fra (10) (q25) and fra (16) (q22) in patients from an institute for the mentally retarded in Italy. We found six cases (1.9%) of fra (10) (q25) and 9 (2.9%) of fra (16) (q22). The study of the fra (X) was restricted to a subgroup of 91 males who did not have other chromosome anomalies or variants, and led to the discovery of 4 fra (X) cases. These 4 had the Martin-Bell syndrome; 3 of them were epileptic and had a characteristic EEG pattern originating during sleep from the temporal lobe not previously described in fra (X) mental retardation.