{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,3]],"date-time":"2026-04-03T21:58:31Z","timestamp":1775253511581,"version":"3.50.1"},"reference-count":12,"publisher":"American Academy of Pediatrics (AAP)","issue":"6","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2021,6,1]]},"abstract":"<jats:p>A 9-month-old boy presented to a community pediatrician with a recent history of failure to thrive. Workup revealed neutropenia and lymphopenia. Subsequent admission for fever and pneumonia revealed an absolute neutrophil count of 860 and absolute lymphocyte count of 214. Lymphopenia affected all lymphocyte subsets and his na\u00efve and memory CD4+ T-cell ratio was inverted for age. Immunoglobulin levels were normal for age, and tetanus and diphtheria antibody titers were protective. The profound lymphopenia raised suspicion for severe combined immunodeficiency (SCID), despite a normal newborn screening by T-cell receptor excision circle analysis. He did not have a previous history of recurrent fevers or infections, had attended day care, and had received all age-appropriate vaccines. He subsequently was diagnosed with Pneumocystis jirovecii pneumonia, adenovirus upper respiratory infection, and rotaviral diarrhea. An enzyme assay revealed absent adenosine deaminase (ADA) activity and elevated erythrocyte deoxyadenosine nucleotides. With genetic sequencing, 2 pathogenic variants in the ADA gene were confirmed. Acute management of ADA-SCID is aimed at restoration of enzyme activity, followed by curative therapy. The patient is currently on immunoglobulin therapy and recombinant ADA (Revcovi), with an excellent immune response, while awaiting sibling hematopoietic cell transplant from a matched sibling. Hypomorphic ADA variants can present with delayed-onset SCID, and some of these patients are missed by SCID newborn screening. A careful review of a complete blood cell count might offer clues and promote confirmatory diagnostic investigation.<\/jats:p>","DOI":"10.1542\/peds.2020-005579","type":"journal-article","created":{"date-parts":[[2021,5,11]],"date-time":"2021-05-11T08:26:57Z","timestamp":1620721617000},"source":"Crossref","is-referenced-by-count":6,"title":["Delayed-Onset ADA1 (ADA) Deficiency Not Detected by TREC Screen"],"prefix":"10.1542","volume":"147","author":[{"given":"Basil M.","family":"Kahwash","sequence":"first","affiliation":[{"name":"Division of Allergy and Immunology, Department of Otolaryngology, College of Medicine, The Ohio State University, Columbus, Ohio; and"},{"name":"Nationwide Children\u2019s Hospital, Columbus, Ohio"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jennifer R.","family":"Yonkof","sequence":"additional","affiliation":[{"name":"Division of Allergy and Immunology, Department of Otolaryngology, College of Medicine, The Ohio State University, Columbus, Ohio; and"},{"name":"Nationwide Children\u2019s Hospital, Columbus, Ohio"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Roshini S.","family":"Abraham","sequence":"additional","affiliation":[{"name":"Nationwide Children\u2019s Hospital, Columbus, Ohio"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Peter J.","family":"Mustillo","sequence":"additional","affiliation":[{"name":"Nationwide Children\u2019s Hospital, Columbus, Ohio"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Rolla","family":"Abu-Arja","sequence":"additional","affiliation":[{"name":"Nationwide Children\u2019s Hospital, Columbus, Ohio"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Hemalatha G.","family":"Rangarajan","sequence":"additional","affiliation":[{"name":"Nationwide Children\u2019s Hospital, Columbus, Ohio"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Rebecca","family":"Scherzer","sequence":"additional","affiliation":[{"name":"Nationwide Children\u2019s Hospital, Columbus, Ohio"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"417","published-online":{"date-parts":[[2021,6,1]]},"reference":[{"issue":"25","key":"2022050912035591400_B1","doi-asserted-by":"crossref","first-page":"2718","DOI":"10.1182\/blood-2017-05-781849","article-title":"Immune reconstitution and survival of 100 SCID patients post-hematopoietic cell transplant: a PIDTC natural history study","volume":"130","author":"Heimall","year":"2017","journal-title":"Blood"},{"issue":"7","key":"2022050912035591400_B2","doi-asserted-by":"crossref","first-page":"729","DOI":"10.1001\/jama.2014.9132","article-title":"Newborn screening for severe combined immunodeficiency in 11 screening programs in the United States. 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