Advances in molecular cytogenetics for the evaluation of mental retardation.

Recent years have witnessed rapid advances in molecular cytogenetics and its impact in studying mental retardation (MR). We review new molecular cytogenetic methods, including interphase fluorescence in situ hyrbridization (FISH), comparative genomic hybridization (CGH), multicolor karyotyping, telomere FISH, primed in situ labeling (PRINS), genotyping, microdissection, and microarray for the evaluation of MR. These new methods are very useful in two major aspects: further characterization of chromosome abnormalities as detected with routine banding analysis, including additions, duplications, deletions, translocations, markers, or complex aberrations; and screening for "hidden" chromosome aberrations in patients with an apparently normal karyotype. These new methods have great diagnostic potential in prenatal, postnatal, and preimplantational settings. Although powerful, at this point, they are primarily research tools in nature. It is essential that these new methods be used in conjunction with standard methods in order to maximize obtainable information for better management of patients with MR.