Article

Newborn Screening for SCID Identifies Patients with Ataxia Telangiectasia

Department of Pediatrics, University of California San Francisco, 513 Parnassus Avenue, HSE 301A, Box 0519, San Francisco, CA, 94143-0519, USA.
Journal of Clinical Immunology (Impact Factor: 2.65). 12/2012; 33(3). DOI: 10.1007/s10875-012-9846-1
Source: PubMed

ABSTRACT PURPOSE: Severe combined immunodeficiency (SCID) is characterized by failure of T lymphocyte development and absent or very low T cell receptor excision circles (TRECs), DNA byproducts of T cell maturation. Newborn screening for TRECs to identify SCID is now performed in several states using PCR of DNA from universally collected dried blood spots (DBS). In addition to infants with typical SCID, TREC screening identifies infants with T lymphocytopenia who appear healthy and in whom a SCID diagnosis cannot be confirmed. Deep sequencing was employed to find causes of T lymphocytopenia in such infants. METHODS: Whole exome sequencing and analysis were performed in infants and their parents. Upon finding deleterious mutations in the ataxia telangiectasia mutated (ATM) gene, we confirmed the diagnosis of ataxia telangiectasia (AT) in two infants and then tested archival newborn DBS of additional AT patients for TREC copy number. RESULTS: Exome sequencing and analysis led to 2 unsuspected gene diagnoses of AT. Of 13 older AT patients for whom newborn DBS had been stored, 7 samples tested positive for SCID under the criteria of California's newborn screening program. AT children with low neonatal TRECs had low CD4 T cell counts subsequently detected (R = 0.64). CONCLUSIONS: T lymphocytopenia in newborns can be a feature of AT, as revealed by TREC screening and exome sequencing. Although there is no current cure for the progressive neurological impairment of AT, early detection permits avoidance of infectious complications, while providing information for families regarding reproductive recurrence risks and increased cancer risks in patients and carriers.

Full-text

Available from: Antonia Kwan, Nov 12, 2014
1 Follower
 · 
169 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Newborn screening (NBS) by quantifying T cell receptor excision circles (TRECs) in neonatal dried blood spots (DBS) enables early diagnosis of severe combined immunodeficiency disease (SCID). In recent years, different screening algorithms for TREC based SCID screening were reported. To systematically review the diagnostic performance of published algorithms for TREC based NBS for SCID. PubMed, EMBASE and the Cochrane Library were systematically searched for case series and prospective cohort studies describing TREC based NBS for SCID. We extracted TREC content and cut-off values, number of retests, repeat DBS and referrals, and type and number of typical SCID and other T cell lymphopenia (TCL) cases. We calculated positive predictive value (PPV), test sensitivity and SCID incidence. Thirteen studies were included, re-confirming 89 known SCID cases in case series and reporting 53 new SCID cases in 3.15 million newborns. In case series, the sensitivity for typical SCID was 100 %. In the prospective cohort studies, SCID incidence was ~1.7:100,000, re-test rate was 0.20-3.26 %, repeat DBS rate 0.0-0.41 % and referral rate 0.01-1.35 %. PPV within the five largest cohorts was 0.8-11.2 % for SCID and 18.3-81.0 % for TCL. Individual TREC contents in all SCID patients was <25 TRECs/μl (except in those evaluated with the New York State assay). The sensitivity of TREC based NBS for typical SCID was 100 %. The TREC cut-off score determines the percentage of non-SCID TCL cases detected in newborn screening for TCL. Adapting the screening algorithm for pre-term/ill infants reduces the amount of false positive test results.
    Journal of Clinical Immunology 04/2015; DOI:10.1007/s10875-015-0152-6 · 2.65 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The development of a T-cell receptor excision circle (TREC) assay utilizing dried blood spots in universal newborn screening has allowed the early detection of T-cell lymphopenia in newborns. Diagnosis of severe combined immunodeficiency (SCID) in affected infants in the neonatal period, while asymptomatic, permits early treatment and restoration of a functional immune system. SCID was the first immunodeficiency disease to be added to the Recommended Uniform Screening Panel of Core Conditions in the United States in 2010, and it is now implemented in 26 states in the U.S. This review covers the development of newborn screening for SCID, the biology of the TREC test, its current implementation in the U.S., new findings for SCID in the newborn screening era, and future directions. Copyright © 2015 Elsevier Inc. All rights reserved.
    Seminars in perinatology 04/2015; 39(3). DOI:10.1053/j.semperi.2015.03.004 · 2.42 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Severe combined immunodeficiency (SCID) encompasses a group of disorders characterized by reduced or absent T-cell number and function and identified by newborn screening utilizing T-cell receptor excision circles (TRECs). This screening has also identified infants with T lymphopenia who lack mutations in typical SCID genes. We report an infant with low TRECs and non-SCID T lymphopenia, who proved upon whole exome sequencing to have Nijmegen breakage syndrome (NBS). Exome sequencing of DNA from the infant and his parents was performed. Genomic analysis revealed deleterious variants in the NBN gene. Confirmatory testing included Sanger sequencing and immunoblotting and radiosensitivity testing of patient lymphocytes. Two novel nonsense mutations in NBN were identified in genomic DNA from the family. Immunoblotting showed absence of nibrin protein. A colony survival assay demonstrated radiosensitivity comparable to patients with ataxia telangiectasia. Although TREC screening was developed to identify newborns with SCID, it has also identified T lymphopenic disorders that may not otherwise be diagnosed until later in life. Timely identification of an infant with T lymphopenia allowed for prompt pursuit of underlying etiology, making possible a diagnosis of NBS, genetic counseling, and early intervention to minimize complications.
    Journal of Clinical Immunology 02/2015; DOI:10.1007/s10875-015-0136-6 · 2.65 Impact Factor