Among the few SCID and T cell deficient children we have NBS-NGS gene panel tested here, we have found various immunodeficiencies with multiple genetic causes (IL2RG, RAG2, RMRP, IKZF1, CHD7, DCLRE1C, JAK3), with different inheritance patterns (AR, AD, de novo, XL) and mutation types (i.e., CNVs in DiGeorge syndrome, intragenic IKZF1 deletion and larger chromosomal aberrations such as Trisomy 21). This evidence concerns the gene IKZF1 and trisomy 21.