A late preterm infant with lymphopenia.

The newborn screen for severe combined immunodeficiency (SCID) uses real-time quantitative polymerase chain reaction for T-cell receptor excision circles and is highly sensitive for SCID. However, T-cell lymphopenia from other primary and secondary causes, such as DiGeorge syndrome, prematurity, thymic involution from stress, and thymectomy during cardiac surgery, is also detected. We present a newborn girl with T-cell lymphopenia of unknown etiology detected via abnormal newborn screen.