Major chromosome abnormalities are present in 0.65% of all neonates. Fluorescent in situ hybridization (FISH) is useful in diagnosing micro-deletion and micro-duplication syndromes that would otherwise be difficult to diagnose using standard cytogenetics [1,2].

Fluorescent in situ hybridization is the “bridge” be­tween standard cytogenetics and molecular genetics. An increased number of human diseases and syndromes are being found to result from micro-duplications and micro-deletions arising from meiotic recombination between homologous repeats on the same chromosome. The FISH technique helps cytogeneticists to distinguish more details in human chromosomes and brought “color” into cyto­genetics. Quite a few micro-deletions and micro-duplica­tions of human chromosomes have been discovered during the last two decades, and most of them characterize well known genetic syndromes.

These submicroscopic abnormalities are distinguished as “interstitial” and “terminal” according to their position from the end of the chromosome, and “proximal” and “distal” according to their distance from the centromere. Recently, a new category located close to the telomere has been added to the above and is called “terminal” or “sub­telomeric” chromosome micro-abnormalities. Chromo­some micro-deletions and micro-duplications are often associated with certain clinical features. This study docu­ments some well recognized genetic syndromes which are demonstrated in Tables 1 and 2.