Primary immunodeficiencies are intrinsic defects in the immune system that encompass more than 350 disease entities, including phagocyte disorders, complement deficiencies, T cell defects, and antibody deficiencies. They are frequently accompanied by a propensity to autoimmunity and/or immune dysregulation. There are wide variations in the frequency and distribution of PIDDs among populations from different ethnic and geographic backgrounds.

Although infants with Severe Combined Immunodeficiency (SCID) appear healthy at birth, they are at risk of fatal outcome unless diagnosed and treated within the first few months of life. Unfortunately, among these infants only those who have had a recognized family history of SCID, which is fewer than 20% of all cases, could have the diagnosis made early. The early diagnosis of congenital immunodeficiencies, which is essential for optimal management and improved outcomes in terms of organ damage and life-threatening infections, is only possible through institution of population-based neonatal screening. In immunological terms, SCID can be detected early in newborns by quantifying T-cell Receptor Excision Circles (TRECs) in Guthrie card Dried Blood Spots (DBS), which are are small circles of DNA created during the recombination of T-cell receptor genes, using a real time quantitative PCR. Congenital B cell lymphopenia, on the other hand, can be identified by screening for kappa-deleting recombination excision circles (KREC) , the circular by-product of B cell immunoglobulin kappa gene rearrangement in DBS. The advantages for including KREC screening in national programs is to aid in the identification of children with X-linked agammaglobulinemia (XLA), late onset Adenosine Deaminase (ADA) deficiency, some patients with Nijmegen-breakage syndrome (NBS), and other selected forms of PIDDs which may otherwise remain undetected by TREC screening alone. Similarly, the TREC test also has secondary targets including non-SCID immunodeficiencies, in which the circulating naïve T cells are deficient, such as DiGeorge syndrome, trisomy 21 and CHARGE syndrome, as well as non-immune problems such as vascular leakage, chylous effusions or congenital leukemia.

Neonatal screening for PIDDs has been an effective public health measure and a strategy for advancing clinical research. For instance, it has been instrumental in uncovering an unbiased incidence of SCID (1 in 58,000 births), which is significantly higher than the previous estimate (1 in 100,000). Moreover, early diagnosis of PIDDs in patients enables early treatment options such as stem cell transplantation. This Research Topic aims to address the current status, limitations and unmet needs of newborn screening for PIDDs. The scope will comprise all possible immunological measures of screening with attention to cost effectiveness and global applicability across ethnicities and geographies.

We aim to draw the attention of immunologists, health care workers and policy makers towards the urgent global need for neonatal screening for PIDDs. We welcome Original Research articles, Systematic Reviews, Reviews, Mini-reviews, Case Reports, Clinical Trials, and Perspective Articles targeted towards research on screening for SCID, XLA, and other PIDDs including immune dysregulation disorders.

We would particularly like to focus on, but not limit to, the following:

1. Current status, limitations and unmet needs of newborn screening for PIDDs
2. Immunological biomarkers of PIDDs in neonates
3. Novel immunological diagnostic approaches for early detection of PIDDs in neonates such as
  a. TREC and TREC/KREC-based screening
  b. Protein-based biomarker assays
  c. Targeted sequencing
  d. Next generation sequencing including whole genome sequencing
  e. Microscopy-based analysis of immune cells
4. Animal model systems for development of screening methods for PIDDs in neonates
5. Clinical studies covering population-wide applications of these novel screening methods
6. Public health implications of institutionalizing screening for PIDDs in Neonates

Topic Editor Prof. Lennart Hammarström holds equity in ImmunoIVD. All other Topic Editors declare no competing interests with regards to the Research Topic subject.

Important Note: All contributions to this Research Topic must be within the scope of the section and journal to which they are submitted, as defined in their mission statements. Frontiers reserves the right to guide an out-of-scope manuscript to a more suitable section or journal at any stage of peer review.