Samples with persistently low TRECs and normal Beta-actin copy number were subjected to 2nd tier testing (qPCR-based copy number analysis for 22q11.2 deletion) to rule out 22q11.2 deletion syndrome, and Proton-Ion Torrent (NGS)-based targeted primary immunodeficiency genes analysis. Here, ACTB is linked to 22q11.2 deletion syndrome.