Use of array CGH in the evaluation of dysmorphology, malformations, developmental delay, and idiopathic mental retardation

The clinical implementation of array comparative genomic hybridization has revolutionized the diagnosis of patients with syndromic or nonsyndromic mental retardation. Multiple studies of hundreds of patients with idiopathic mental retardation, and normal karyotype and/or subtelomeric testing using genome-wide microarray platforms with ∼2000 to >30 000 (tiling-path) interrogating BAC/PAC probes have detected chromosome abnormalities in up to 17% of cases. Surprisingly, some of the pathogenic changes are mosaic and not detectable in conventional karyotyping. Commercially available genome-wide microarrays with >300 000 synthesized oligonucleotide probes enable higher resolution and sensitivity and will probably replace the BAC/PAC arrays in clinical laboratories.