“2q37” identifies a specific bit of DNA: the 37th set of bands at the tip of the long (“q”) arm of chromosome 2. Deletions are cases when genetic information has been missed out. In Sacha’s particular case, around 6 million base pairs are missing.
The effects of deletions like this are very variable, and since 2q37 deletion syndrome is so rare, the scientific literature is based on a small number of cases. But we do know that it is associated with autism-like symptoms, learning disabilities, seizures, loose joints, floppy muscles, and heart and kidney problems. Many of these apply to Sacha.