{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,4]],"date-time":"2026-03-04T14:38:28Z","timestamp":1772635108219,"version":"3.50.1"},"reference-count":26,"publisher":"MDPI AG","issue":"9","license":[{"start":{"date-parts":[[2020,8,29]],"date-time":"2020-08-29T00:00:00Z","timestamp":1598659200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Genes"],"abstract":"<jats:p>Incidental findings on newborn screening (NBS) are results that are not the target of screening within a given NBS program, but rather are found as a result of the screening and resulting diagnostic workup for that target. These findings may not have an immediate clinical impact on the newborn, but are sometimes an additional benefit of NBS programs and may be considered secondary targets of NBS programs. This work describes four case reports that had incidental findings on the NBS, which eventually led to the diagnosis of another metabolic disease instead of the one that was initially suspected. The first case was a new defect in the cationic amino acid transporter-2 (CAT-2), which was oriented as an arginase-1 deficiency in the newborn. The second case was a maternal glutaric aciduria type 1 (GA-1) that mimicked a carnitine transporter deficiency in the newborn. The third report was a case of lysinuric protein intolerance (LPI), which appeared as high levels of citrulline on the NBS. The fourth case was a mother with homocystinuria that was diagnosed during the biochemical study of vitamin B12 status. All cases provide new or interesting data that will help guide differential diagnosis in the future.<\/jats:p>","DOI":"10.3390\/genes11091018","type":"journal-article","created":{"date-parts":[[2020,8,30]],"date-time":"2020-08-30T06:06:22Z","timestamp":1598767582000},"page":"1018","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":9,"title":["Metabolic Serendipities of Expanded Newborn Screening"],"prefix":"10.3390","volume":"11","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-6789-1563","authenticated-orcid":false,"given":"Raquel","family":"Yahyaoui","sequence":"first","affiliation":[{"name":"Laboratory of Metabolic Disorders, Hospital Regional Universitario de M\u00e1laga, 29011 M\u00e1laga, Spain"},{"name":"Instituto de Investigaci\u00f3n Biom\u00e9dica de M\u00e1laga-IBIMA, 29010 M\u00e1laga, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4008-3747","authenticated-orcid":false,"given":"Javier","family":"Blasco-Alonso","sequence":"additional","affiliation":[{"name":"Instituto de Investigaci\u00f3n Biom\u00e9dica de M\u00e1laga-IBIMA, 29010 M\u00e1laga, Spain"},{"name":"Pediatric Gastroenterology, Hepatology and Nutrition Unit, Hospital Regional Universitario de M\u00e1laga, 29011 M\u00e1laga, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Montserrat","family":"Gonzalo-Mar\u00edn","sequence":"additional","affiliation":[{"name":"Instituto de Investigaci\u00f3n Biom\u00e9dica de M\u00e1laga-IBIMA, 29010 M\u00e1laga, Spain"},{"name":"Endocrinology and Nutrition Unit, Hospital Regional Universitario de M\u00e1laga, 29011 M\u00e1laga, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Carmen","family":"Benito","sequence":"additional","affiliation":[{"name":"Department of Genetics, Hospital Regional Universitario de M\u00e1laga, 29011 M\u00e1laga, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Juliana","family":"Serrano-Nieto","sequence":"additional","affiliation":[{"name":"Pediatric Gastroenterology, Hepatology and Nutrition Unit, Hospital Regional Universitario de M\u00e1laga, 29011 M\u00e1laga, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Inmaculada","family":"Gonz\u00e1lez-Gallego","sequence":"additional","affiliation":[{"name":"Unit of Metabolic Disorders, Centro de Bioqu\u00edmica y Gen\u00e9tica Cl\u00ednica, Hospital Universitario Virgen de la Arrixaca, 30120 Murcia, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1785-4988","authenticated-orcid":false,"given":"Pedro","family":"Ruiz-Sala","sequence":"additional","affiliation":[{"name":"Centro Diagn\u00f3stico de Enfermedades Moleculares (CEDEM), Centro de Biolog\u00eda Molecular, Universidad Aut\u00f3noma de Madrid, CIBERER, IdiPAZ, 28049 Madrid, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3190-1958","authenticated-orcid":false,"given":"Bel\u00e9n","family":"P\u00e9rez","sequence":"additional","affiliation":[{"name":"Centro Diagn\u00f3stico de Enfermedades Moleculares (CEDEM), Centro de Biolog\u00eda Molecular, Universidad Aut\u00f3noma de Madrid, CIBERER, IdiPAZ, 28049 Madrid, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7578-241X","authenticated-orcid":false,"given":"Domingo","family":"Gonz\u00e1lez-Lamu\u00f1o","sequence":"additional","affiliation":[{"name":"Department of Pediatrics, University of Cantabria-University Hospital Marqu\u00e9s de Valdecilla, 39008 Santander, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2020,8,29]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"71","DOI":"10.1002\/mas.21463","article-title":"Expanded newborn screening by mass spectrometry: New tests, future perspectives","volume":"35","author":"Ombrone","year":"2016","journal-title":"Mass Spectrom. 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