Use of FISH technique in the diagnosis of chromosomal syndromes.

Major chromosome abnormalities are present in 0.65% of all neonates. Fluorescent in situ hybridization (FISH) is useful in diagnosing microdeletion syndromes that would otherwise be difficult to diagnose using standard cytogenetics. In this study, we used FISH analysis in the laboratory diagnosis of 4 patients with Prader-Willi Syndrome [del(15)(q11.2q12)], 4 patients with DiGeorge syndrome [del(22)(q11.2q11.23)] and 4 patients with Williams syndrome [del(7)(q11.23q11.23)]. High-resolution chromosome analysis in all these patients was either normal or inconclusive but all the syndromes were confirmed using FISH. We recommend cytogenetic analysis should always be supplemented with FISH to diagnose all cases suspected of a microdeletion syndrome.