Newborn screening for SCID: where are we now?

Newborn screening (NBS) for severe T-cell lymphopenia/severe combined immunodeficiency using the T-cell receptor excision circle assay continues to expand in the USA and worldwide. Here, we will review why severe combined immunodeficiency is an excellent case for NBS, the outcomes of the first 6 years of screening, and dilemmas surrounding screening and management of infants detected by NBS. We will also discuss the future of NBS for primary immunodeficiencies.