YCLIM-07307; No. of pages: 2; 4C: Clinical Immunology (2014) xx, xxx–xxx
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Clinical Immunology www.elsevier.com/locate/yclim
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LETTER TO THE EDITOR
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KEYWORDS SCID; ZAP70; TREC; Newborn
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To the Editor
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The outcomes of patients diagnosed with Severe Combined Immunodeficiency (SCID) have improved dramatically in recent years with advances in hematopoietic stem cell transplantation. Early diagnosis of SCID before the first severe infection episode represents a critical factor for success after transplant. For this reason, there is advocacy to introduce SCID as part of newborn screening (NBS) programs. The measurement of T-cell receptor excision circles (TRECs) which represents an approximation of thymic output of naïve T cells used for many years in patients with HIV-1 [1] and hematologic malignancies [2] represents an ideal method for the screening of patients with decreased circulating naïve T cells. Introduced initially as a pilot program in Wisconsin [3], TREC-based NBS for SCID has now been recommended for the Uniform Screening panel by the USA Advisory Committee on Heritable Disorders and implemented in various USA states with published reports [3–6] demonstrating encouraging results in terms of early detection of SCID prior to the development of life threatening infections. Given that certain subtypes of SCID, specifically ‘leaky’ SCID, are characterized by early opportunistic infections with persistence of circulating immune T cells, there are concerns raised in the literature [7] regarding the ability of the TREC-based newborn screening to detect all types of SCID. We present a case of a previously healthy term infant male of Mennonite descent who presented at 7 months of age with a rhinovirus pneumonia complicated by severe acute respiratory distress syndrome. Laboratory investigations are summarized in Table 1 and included normal IgG levels but increased IgA and IgM levels and a decreased total
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This case emphasizes a limitation of TREC-based NBS to detect ZAP70 deficiency. Alternative screening methods will be required to allow early detection in populations known to harbor this particular mutation.
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Disclosure of potential conflict of interest
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The authors have declared that they have no conflict of interest.
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lymphocyte count (1700 cells/μL) with normal numbers of circulating CD4+ cells (1650 cells/μL) but markedly decreased CD8+ cell numbers (20 cells/μL). Lymphocyte response to the T-cell mitogen phytohemagglutinin (PHA) was also markedly reduced. In light of the clinical presentation, ethnic background and near absence of CD8 cells, the ZAP70 gene was sequenced and revealed a homozygous mutation previously described in the Canadian Mennonite community (IVS12-11GNA(g.24417GNA)) [8]. In order to determine whether the TREC-based NBS would have allowed early diagnosis of SCID, we submitted a sample from the patient's NBS card obtained at birth, and a second sample obtained at age 9 months. The TREC level (copy number per 3 μL), determined by real time polymerase chain reaction, was above the established NBS cutoff on the birth sample (148, normal range: 82–3316) but was not detectable at age 9 months. We describe the case of a patient with a subtype of SCID characterized by persistent circulating immune T cells, which would not have been detected by a TRECbased NBS program. We believe that the description of this case is clinically relevant as it illustrates an important limitation of the current method of newborn screening for SCID. Although the TREC levels are usually low in newborns with SCID caused by mutations in RAG1/2, ADA, CD3D, JAK3, IL2RA, and LIGASE4 [7], less is known about more rare forms of SCID. Two recent publications [7,9] demonstrated that TREC levels were decreased in patients with ZAP70 deficiency at the time of clinical presentation but the TREC levels at birth were not recorded.
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Limitation of TREC-based newborn screening for ZAP70 Severe Combined Immunodeficiency
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http://dx.doi.org/10.1016/j.clim.2014.04.015 1521-6616/© 2014 Published by Elsevier Inc. Please cite this article as: S. Grazioli, et al., Limitation of TREC-based newborn screening for ZAP70 Severe Combined Immunodeficiency, Clin. Immunol. (2014), http://dx.doi.org/10.1016/j.clim.2014.04.015
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Table 1
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Lymphocyte counts (cells/μL) CD3+ CD3+CD4+ CD3+CD8+ CD4+/CD8+ ratio Mitogen stimulation (proliferation count) PHA response PWM SAC Thymic output TREC (copy number 148 per 3 μL) Immunoglobulins IgG (g/L) IgA (g/L) IgM (g/L)
t1:19 t1:20 t1:21 t1:22 t1:23
The in vitro mitogen response to phytohemagglutinin (PHA), pokeweed mitogen (PWM) and Staphylococcus aureus Cowan I (SAC) was measured after 5 days of culture. T-cell receptor excision circles (TRECs) were measured by RT-PCR after DNA extraction on Newborn Screening (NBS) Card.
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82–3316
3.5–9.8 0.08–0.8 0.06–1.45
References
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[1] M.D. Hazenberg, S.A. Otto, J.W. Cohen Stuart, M.C. Verschuren, J.C. Borleffs, C.A. Boucher, R.A. Coutinho, J.M. Lange, T.F. Rinke de Wit, A. Tsegaye, J.J. van Dongen, D. Hamann, R.J. de Boer, F. Miedema, Increased cell division but not thymic dysfunction rapidly affects the T-cell receptor excision circle content of the naive T cell population in HIV-1 infection, Nat. Med. 6 (2000) 1036–1042. [2] X. Chen, R. Barfield, E. Benaim, W. Leung, J. Knowles, D. Lawrence, M. Otto, S.A. Shurtleff, G.A. Neale, F.G. Behm, V. Turner, R. Handgretinger, Prediction of T-cell reconstitution by assessment of T-cell receptor excision circle before allogeneic hematopoietic stem cell transplantation in pediatric patients, Blood 105 (2005) 886–893. [3] N.M. Chase, J.W. Verbsky, J.M. Routes, Newborn screening for SCID: three years of experience, Ann. N. Y. Acad. Sci. 1238 (2011) 99–105. [4] A. Kwan, J.A. Church, M.J. Cowan, R. Agarwal, N. Kapoor, D.B. Kohn, D.B. Lewis, S.A. McGhee, T.B. Moore, E.R. Stiehm, M. Porteus, C.P. Aznar, R. Currier, F. Lorey, J.M. Puck, Newborn screening for severe combined immunodeficiency and T-cell lymphopenia in California: results of the first 2 years, J. Allergy Clin. Immunol. 132 (2013) 140–150.
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Serge Grazioli Mary Bennett Pediatric Intensive Care Unit, Department of Pediatrics, British Columbia Children's Hospital, University of British Columbia, Vancouver, BC, Canada
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Kyla J. Hildebrand Division of Allergy and Immunology, Department of Pediatrics, British Columbia Children's Hospital, Child & Family Research Institute, University of British Columbia, Vancouver, BC, Canada
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At At presentation Reference birth (9 months of age) range
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[5] J. Verbsky, M. Thakar, J. Routes, The Wisconsin approach to newborn screening for severe combined immunodeficiency, J. Allergy Clin. Immunol. 129 (2012) 622–627. [6] J.E. Hale, F.A. Bonilla, S.Y. Pai, J.L. Gerstel-Thompson, L.D. Notarangelo, R.B. Eaton, A.M. Comeau, Identification of an infant with severe combined immunodeficiency by newborn screening, J. Allergy Clin. Immunol. 126 (2010) 1073–1074. [7] C.M. Roifman, R. Somech, F. Kavadas, Linda Pires, Amit Nahum, Ilan Dalal, Eyal Grunebaum, Defining combined immunodeficiency, J. Allergy Clin. Immunol. 130 (2012) 177–183. [8] E. Arpaia, M. Shahar, H. Dadi, A. Cohen, C.M. Roifman, Defective T cell receptor signaling and CD8+ thymic selection in humans lacking zap-70 kinase, Cell 76 (1994) 947–958. [9] Vy Hong-Diep Kim, Luis Murguia, Tal Schechter, Eyal Grunebaum, C.M. Roifman, Emergency treatment for zeta chain-associated protein of 70 kDa (ZAP70) deficiency, J. Allergy Clin. Immunol. 131 (2013) 1233–1235.
Immune profiles.
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Hilary Vallance Department of Pathology, British Columbia Children's Hospital, Vancouver, BC, Canada
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Stuart E. Turvey Anne K. Junker* Division of Allergy and Immunology, Department of Pediatrics, British Columbia Children's Hospital, Child & Family Research Institute, University of British Columbia, Vancouver, BC, Canada ⁎Corresponding author at: Division of Allergy and Immunology, Department of Pediatrics, British Columbia Children's Hospital, Child & Family Research Institute, University of British Columbia, Room K4-223, 4480 Oak Street, Vancouver, BC V6H 3V4, Canada. E-mail address:
[email protected] (A.K. Junker).
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Please cite this article as: S. Grazioli, et al., Limitation of TREC-based newborn screening for ZAP70 Severe Combined Immunodeficiency, Clin. Immunol. (2014), http://dx.doi.org/10.1016/j.clim.2014.04.015
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