Inclusion Criteria: * Patient to 47 months * SCID patients with confirmed biallelic mutations in the Artemis (DCLRE1C) gene even in the case of leaky forms characterised by a residual activity * Absence of an HLA genoidentical donor or without rapidly available HLA-compatible unrelated donor (within six weeks of diagnosis) * The patient can be treated by gene therapy without delay in case of active life threatening infections compromising the short-term prognosis and for which the delay in finding a phenoidentical donor is incompatible with the patient's condition of health. Active life threatening infections are defined as: viral respiratory infection, CMV infection, adenovirus infection, disseminated BCGitis or other infections grade ≥ 4 according to CTCAE scale * Beneficiary of a social security scheme * Parental, guardian's patient signed informed consent. Exclusion Criteria * Unwillingness to return for follow-up during the first 2 years study and the long term follow-up * HIV-1 or 2 or HTLV1 infections * Hypersensitivity to G-CSF, busulfan or Fludarabine * Unable to tolerate general anesthesia and/or marrow harvest or peripheral blood stem cell collection (apheresis) or insertion of central venous catheter.