Newborn screening for severe combined immunodeficiency does not identify bare lymphocyte syndrome

In May 2010, SCID was recommended to be added to the panel of genetic disorders in the national uniform newborn screening (NBS) program.1 SCID screening involves the measurement of T-cell receptor excision circles (TRECs), by-products of T-cell receptor rearrangement that reflect the robustness of T-cell production in the thymus; low blood levels of TRECs suggest profound T lymphopenia and are used to identify newborns for further evaluation. Hematopoietic stem cell transplant remains the only curative treatment, but the increased incidence and severity of graft-versus-host disease in association with pretransplant viral infections emphasize the importance of early diagnosis and intervention.6 In addition, the identification of 2 cases in California within a 6-month period and in patients of an ethnic background not usually associated with this disease suggest that MHC class II deficiency may not be as rare as previously considered.