FISH, DiGeorge, Velocardiofacial Syndrome

Laboratory assay overview

This test uses fluorescence in situ hybridization (FISH) technology to detect microdeletions in the chromosome 22q11.2 region when there is clinical suspicion of 22q11.2 deletion syndrome. Chromosome 22q11.2 deletions are associated with conditions including DiGeorge syndrome (DGS) and velocardiofacial syndrome (VCFS). 22q11.2 deletion syndrome cannot be detected by conventional or high-resolution chromosome analysis (karyotyping) [1,2]. Common clinical features associated with 22q11.2 deletion syndrome include congenital heart disease (64%); palate deformities (67%), especially cleft palate; learning difficulties (70%-90%); immune deficiency (77%); hypocalcemia (50%); gastrointestinal anomalies; renal anomalies (16%); skeletal abnormalities; and ocular abnormalities [3]. The FISH DGS/VCFS test is generally ordered for individuals with clinical suspicion of 22q11.2 deletion syndrome. This FISH test can also be performed on prenatal specimens, such as chorionic villus sampling and amniotic fluid specimens [4]. Note: Most deletions associated with 22q11.2 deletion syndrome can be detected with FISH. However, some affected individuals have smaller, atypical, nested deletions that cannot be detected with FISH but can be detected with chromosomal microarray analysis (CMA). The results of this test should be interpreted in the context of pertinent clinical and family history and physical examination findings. References 1. Novelli A, et al. Molec Cellular Probes. 1999;13(4):303-307. 2. International 22q11.2 Foundation. Deletion vs. Duplication. Accessed August 27, 2021. https://22q.org/what-is-22q/deletion-vs-duplication/ 3. McDonald-McGinn DM, et al. 22q11.2 deletion syndrome. In: Adam MP, et al., ed. GeneReviews®. University of Washington; September 23, 1999. Accessed August 27, 2021. https://www.ncbi.nlm.nih.gov/books/NBK1523/ 4. Driscoll DA. Genet Med. 2001;3(1):14-18.