[Subtelomeric rearrangements in cryptogenic mental retardation].

INTRODUCTION:Mental retardation affects 3% of the population, the origin of which cannot be established in 50% of cases. Subtelomeric rearrangements, not detected by routine cytogenetic studies, might explain some cases of unknown cause. PATIENTS AND METHODS:A study was conducted on 200 subjects with unexplained mental retardations using multiplex ligation dependent probe amplification (MLPA). Abnormal findings were confirmed by fluorescent in situ hybridization (FISH) and/or comparative genomic hybridization technology (CGH-array). RESULTS:A subtelomeric aberration was identified in 9 patients. Eight were «de novo»; one was inherited from a phenotypically normal parent. There was a statistically significant association with the presence of more than one dysmorphic feature or with intrauterine growth retardation, but not with the severity of retardation or epilepsy. CONCLUSIONS:Subtelomeric rearrangements explained 4.5% of cases of mental retardation in our series. The presence of more than one dysmorphic feature or intrauterine uterine growth retardation increases the probability of this type of chromosomal aberration.