LIG4 and Omenn syndrome: Omenn syndrome has been well described for a number of genes including recombination activating gene 1 and 2 (RAG1/RAG2) (103), ARTEMIS (DCLRE1C) (104), adenosine deaminase (ADA) (105, 106), IL-7 receptor alpha (IL7RA) (107), DNA ligase 4 (LIG4) (108), ZAP70 (75), adenylate kinase 2 (AK2) (109), and CARD11 (110).