As a next step, comprehensive genetic testing of 26 genes associated with SCID or combined-immunodeficiency (ADA, AK2, ATM, CD3D, CD3E, CD3Z, CORO1A, DCLRE1C, DOCK8, FOXN1, IL2RG, IL7R, JAK3, LIG4, NHEJ1, ORAI1, PNP, PTPRC, PRKDC, RAC2, RAG1, RAG2, RMRP, STIM1, TBX1, and ZAP-70) was pursued and was unrevealing. Here, CD3D is linked to severe combined immunodeficiency.