Sixpatients had ADA deficiency, 3 had IL2RG deficiency, 3 had CD3 Delta deficiency, 2 had Artemis deficiency (affecting DCLRE1C), and 1 each had variants impacting NHEJ1, TRAC, RAC2, and RMRP. Here, ADA is linked to severe combined immunodeficiency due to DCLRE1C deficiency.