Phenotypic variants in children with subtle chromosomal rearrangements

In recent years, subtelomeric rearrangements have been identified as a major cause of mental retardation. Around 200 chromosomal abnormalities have been detected in more then 3600 patients tested so far. Some of the subtelomere deletions found result in a specific phenotype. However, the majority of cases with subtelomeric defects lack a characteristic phenotype, since such cases have only been reported sporadically. Furthermore, the clinical outcome of many cases is affected by a genotypic constellation in which similar telomeric deletions are associated with additional telomeric duplications which differ in the individual patients.

We report on a large multicenter study for children with idiopathic mental retardation to evaluate the occurrence of subtelomeric rearrangements in relation to detailed clinical parameters including family history, anthropometric measurements, neurological data and developmental scales. Our preliminary data identified more chromosomal defects in all grades of mental retardation then previously reported, suggesting that this study for the first time may provide phenotype-genotype correlations for affected children.