Natural history of infants with non-SCID T cell lymphopenia identified on newborn screen

Newborn screening (NBS) for severe combined immunodeficiency (SCID) can identify infants with non-SCID T cell lymphopenia (TCL). The purpose of this study was to characterize the natural history and genetic findings of infants with non-SCID TCL identified on NBS. We analyzed data from 80 infants with non-SCID TCL in the mid-Atlantic region between 2012 and 2019. 66 patients underwent genetic testing and 41 (51%) had identified genetic variant(s). The most common genetic variants were thymic defects (33%), defects with unknown mechanisms (12%) and bone marrow production defects (5%). The genetic cohort had significantly lower median initial CD3+, CD4+, CD8+ and CD4/CD45RA+ T cell counts compared to the non-genetic cohort. Thirty-six (45%) had either viral, bacterial, or fungal infection; only one patient had an opportunistic infection (vaccine strain VZV infection). Twenty-six (31%) of patients had resolution of TCL during the study period.

Newborn screening for SCID: lessons learned

INTRODUCTION

Newborn screening (NBS) for Severe combined immunodeficiency (SCID)/severe T cell lymphopenia (sTCL) is being increasingly used worldwide.

AREAS COVERED

In this manuscript we will discuss the following: 1) The rationale for screening newborns for SCID/sTCL; 2) The scientific basis for the use of the T cell receptor excision circle (TREC) assay in screening newborns for SCID/sTCL; 3) The published outcomes of current NBS programs. Expert commentary: 4) Some of the ethical dilemmas that occur when screening newborns for SCID. Finally, we will discuss the future directions for expanding NBS to include other primary immunodeficiencies.