Chromosomal microarrays work by testing for the presence of two copies of 22q13 on chromosome 22. This technique is more sensitive than tests previously used because it can detect the loss of chromosomal material in very small regions of the chromosome. If your child has a 22q13 deletion, the 22q13 region will be present on the normal chromosome but absent on the deleted chromosome.
Another test for 22q deletions is called the Fluorescence In Situ Hybridization Test (FISH). The FISH test involves a DNA probe that is specific for the tip of the long arm of chromosome 22. Like chromosomal microarrays, this probe checks whether the 22q13 segment is present or absent.
If the CMA does not reveal a deletion, individuals can choose to receive Whole Exome Sequencing (WES), a cutting-edge technology that sequences the DNA and will determine whether a very small mutation, as opposed to a deletion, is present that disrupt the functioning of the SHANK3 gene.
Genetic testing is performed using a blood sample that is drawn from a vein in the arm using a small needle. Parents also need to undergo some genetic testing to assess recurrence risk in the family.