MTOR and Down syndrome: For example, a patient identified to have an IEI affecting JAK-STAT signalling pathways such as STAT1 or STAT3 gain-of-function mutations can be offered targeted therapies abrogating abnormal signalling, and those with activated phosphoionositide 3-kinase delta syndrome may be offered specific therapies with mammalian target of rapamycin (mTOR) inhibitors or newly developed targeted small-molecule drugs [20].