from 2020 more than 30 gene therapy clinical trials on monogenic diseases (phase I to phase III) were registered, including X -linked SCID (X1-SCID) (ILR2G), ADA-SCID (ADA), Wiskott- Aldrich (WAS), X-CGD (CYBB), Leukocyte adhesion deficiency (CD18) and Artemis-deficiency (ART) SCID (DCLRE1C) (30). Here, ADA is linked to severe combined immunodeficiency due to DCLRE1C deficiency.