Diagnosis of cryptic chromosome aberrations

Background: Cryptic chromosome aberrations, i.e. those that are not observed by routine chromosome analysis (G-banding), can cause a plethora of developmental abnormalities, usually at least a combination of various dysmorphic signs and mental retardation.

Methods: We present the current molecular cytogenetic methods for detection of cryptic chromosome aberrations, with special emphasis on comparative genomic hybridisation (CGH), a DNA-based screening method.

Results: Using comparative genomic hybridisation with high-resolution analysis, we were able to detect a chromosome aberration in 10 % of patients found to have normal karyotypes by standard chromosome analysis.

Conclusions: Though the sensitivity of comparative genomic hybridisation is still insufficient for finding a deletion in most of the well-known microdeletion syndromes, the diagnostic yield of genomic imbalances is better than for all other laboratory investigations except routine G-banding.