The Harmony® Test, analyses the risk of DiGeorge syndrome (Microdeletion 22q11.2) in the unborn child.
The DiGeorge syndrome is caused by a submicroscopic deletion in chromosome 22. In most cases, the size of the deletion is about 3 megabases (MB), but in about 10-15% of cases it can be even smaller (1.5 MB or less.)
In 90% of the cases DiGeorge syndrome develops “de novo”, by a spontaneous genetic mutation not inherited from the parents 1.
The clinical severity of the DiGeorge syndrome varies depending on the size and position of the deletion 2.
The screening for DiGeorge syndrome by the Harmony® Test determines the probability for the presence of the genetic disorder, however, it is not able to ascertain the clinical severity of the microdeletion.
In singleton pregnancies the analysis for DiGeorge syndrome can be added to all other test options of the Harmony® Test. The positive predictive value (PPV) is 5%. As in screening for trisomies, screening for DiGeorge syndrome can lead to false-positive results. Therefore, a report indicating a high risk for the microdeletion has to be confirmed by an invasive diagnostic procedure (array-CGH), before further actions can be taken.
- McDonald-McGinn D.M., Tonnesen M.K., Laufer-Cahana A., Finucane B., Driscoll D.A., Emanuel B.S., Zackai E.H. (2001) Phenotype of the 22q11.2 deletion in individuals identified through an affected relative: cast a wide FISHing net! Genet Med. 2001 Jan-Feb;3(1):23-9. ↩
- Grati F.R., Molina Gomes D., Ferreira J.C., Dupont C., Alesi V., Gouas L., Horelli-Kuitunen N., Choy K.W., García-Herrero S., de la Vega A.G., Piotrowski K., Genesio R., Queipo G., Malvestiti B., Hervé B., Benzacken B., Novelli A., Vago P., Piippo K., Leung T.Y., Maggi F., Quibel T., Tabet A.C., Simoni G., Vialard F., Prevalence of recurrent pathogenic microdeletions and microduplications in over 9500 pregnancies. Prenat Diagn. 2015 Aug;35(8):801-9. ↩