When Screening for Severe Combined Immunodeficiency (SCID) with T Cell Receptor Excision Circles Is Not SCID: a Case-Based Review

David Buchbinder, Jolan E. Walter, Manish J. Butte, Wan Yin Chan, Maria Chitty Lopez, Victoria R. Dimitriades, Morna J. Dorsey, Diane J. Nugent, Jennifer M. Puck, Jasjit Singh, Cathleen A. Collins

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


Newborn screening efforts focusing on the quantification of T cell receptor excision circles (TRECs), as a biomarker for abnormal thymic production of T cells, have allowed for the identification and definitive treatment of severe combined immunodeficiency (SCID) in asymptomatic neonates. With the adoption of TREC quantification in Guthrie cards across the USA and abroad, typical, and atypical SCID constitutes only ~ 10% of cases identified with abnormal TRECs associated with T cell lymphopenia. Several other non-SCID-related conditions may be identified by newborn screening in a term infant. Thus, it is important for physicians to recognize that other factors, such as prematurity, are often associated with low TRECs initially, but often improve with age. This paper focuses on a challenge that immunologists face: the diagnostic evaluation and management of cases in which abnormal TRECs are associated with variants of T cell lymphopenia in the absence of a genetically defined form of typical or atypical SCID. Various syndromes associated with T cell impairment, secondary forms of T cell lymphopenia, and idiopathic T cell lymphopenia are identified using this screening approach. Yet there is no consensus or guidelines to assist in the evaluation and management of these newborns, despite representing 90% of the patients identified, resulting in significant work for the clinical teams until a diagnosis is made. Using a case-based approach, we review pearls relevant to the evaluation of these newborns, as well as the management dilemmas for the families and team related to the resolution of genetic ambiguities.

Original languageEnglish (US)
Pages (from-to)294-302
Number of pages9
JournalJournal of Clinical Immunology
Issue number2
StatePublished - Feb 2021


  • idiopathic T cell lymphopenia
  • Newborn screening
  • secondary T cell lymphopenia
  • syndromes associated with T cell lymphopenia

ASJC Scopus subject areas

  • Immunology and Allergy
  • Immunology


Dive into the research topics of 'When Screening for Severe Combined Immunodeficiency (SCID) with T Cell Receptor Excision Circles Is Not SCID: a Case-Based Review'. Together they form a unique fingerprint.

Cite this