Di George Syndrome - Diagnosis and Testing

Diagnosis and Testing

The 22q11.2 deletion syndrome is diagnosed in individuals with a submicroscopic deletion of chromosome 22 detected by fluorescence in situ hybridization (FISH), BACs-on-Beads technology, Multiplex ligation-dependent probe amplification (MLPA) or Array-comparative genomic hybridization (array-CGH). FISH is done on a blood sample. In FISH one DNA probe from the 22q11.2 chromosomal region is used at a time, while with BACs-on-Beads technology multiple probes from the 22q11.2 region can be used simultaneously. In MLPA testing, various probes for selected regions of 22q11.2 are used to identify microdeletions, however any findings should be further confirmed by other techniques (FISH or array-CGH). Array-CGH is a technique of molecular karyotype where a large number of probes are embedded in a chip in order to screen the entire genome for deletions or dublications. Array-CGH can identify the extend of the microdeletion in 22q11.2 chromosomal region and characterise any missing genes leading to a better evaluation of signs, symptoms and prognosis of the syndrome. Such genetic testing is widely available for the clinical and prenatal testing of the 22q11.2 deletion syndrome. Fewer than 5% of individuals with clinical symptoms of the 22q11.2 deletion syndrome have normal routine cytogenetic studies and negative FISH testing. Some cases of DiGeorge Syndrome have defects in other chromosomes, notably a deletion in chromosome region 10p14. They may have variant deletions of DiGeorge syndrome that may be detectable on a research basis only or with other more advanced clinical testing method.