{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,23]],"date-time":"2026-09-23T07:05:03Z","timestamp":1790147103759,"version":"4.0.1"},"reference-count":8,"publisher":"The Endocrine Society","issue":"10","license":[{"start":{"date-parts":[[2026,9,23]],"date-time":"2026-09-23T00:00:00Z","timestamp":1790121600000},"content-version":"vor","delay-in-days":20,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2026,9,3]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:p>A 76-year-old man presented shortly after knee arthroplasty with malaise, nausea, and severe parathyroid hormone\u2013independent hypercalcemia. Initial laboratory evaluation demonstrated a markedly elevated 25-hydroxyvitamin D concentration (&amp;gt;250\u2005nmol\/L [&amp;gt;100\u2005ng\/mL]; reference &amp;gt;50\u2005nmol\/L [&amp;gt;20\u2005ng\/mL]), suggestive of vitamin D intoxication. However, this diagnosis appeared implausible because the patient used only 400\u2005IU cholecalciferol daily, serum phosphate remained normal, and several Calcium elevation, Renal dysfunction, Anemia and Bone disease features suggested an underlying plasma cell disorder. Further evaluation confirmed symptomatic immunoglobulin A kappa (IgA-\u03ba) multiple myeloma. Repeat measurement of 25-hydroxyvitamin D by liquid chromatography\u2013tandem mass spectrometry (LC-MS\/MS) demonstrated a normal concentration (92\u2005nmol\/L [36.8\u2005ng\/mL]), confirming analytical interference. The falsely elevated result was reproduced in an independent reference laboratory, and 25-hydroxyvitamin D normalized following successful antimyeloma therapy in parallel with a marked reduction in paraprotein concentration. This case highlights the importance of integrating laboratory findings with clinical reasoning and confirms the value of LC-MS\/MS in patients with clinically implausible vitamin D concentrations.<\/jats:p>","DOI":"10.1210\/jcemcr\/luag297","type":"journal-article","created":{"date-parts":[[2026,9,17]],"date-time":"2026-09-17T19:24:52Z","timestamp":1789673092000},"source":"Crossref","is-referenced-by-count":0,"title":["Apparent vitamin D intoxication due to paraprotein interference"],"prefix":"10.1210","volume":"4","author":[{"ORCID":"https:\/\/orcid.org\/0009-0004-9404-6815","authenticated-orcid":false,"given":"Sjaam","family":"Jainandunsing","sequence":"first","affiliation":[{"name":"Department of Internal Medicine, Anna Hospital , Geldrop 5664 EH ,","place":["The Netherlands"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6938-065X","authenticated-orcid":false,"given":"Evert F S","family":"van Velsen","sequence":"additional","affiliation":[{"name":"Department of Internal Medicine, Erasmus MC , Rotterdam 3000 CA ,","place":["The Netherlands"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Pauline","family":"Verschuure","sequence":"additional","affiliation":[{"name":"Department of Clinical Chemistry, Anna Hospital , Geldrop 5664 EH ,","place":["The Netherlands"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Dennis","family":"Willemsen","sequence":"additional","affiliation":[{"name":"Department of Internal Medicine, Anna Hospital , Geldrop 5664 EH ,","place":["The Netherlands"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"80","published-online":{"date-parts":[[2026,9,23]]},"reference":[{"key":"2026092302540753900_luag297-B1","volume-title":"Endotext","author":"Goltzman"},{"issue":"6","key":"2026092302540753900_luag297-B2","doi-asserted-by":"crossref","first-page":"667","DOI":"10.1177\/00045632211013862","article-title":"Prevalence of paraprotein interference in three clinical chemistry analytes in a routine biochemistry laboratory","volume":"58","author":"Graham","year":"2021","journal-title":"Ann Clin Biochem"},{"issue":"6","key":"2026092302540753900_luag297-B3","doi-asserted-by":"crossref","first-page":"716","DOI":"10.1177\/0004563217690175","article-title":"Artefactual 25-OH vitamin D concentration in multiple myeloma","volume":"54","author":"Ong","year":"2017","journal-title":"Ann Clin Biochem"},{"issue":"4","key":"2026092302540753900_luag297-B4","doi-asserted-by":"crossref","first-page":"663","DOI":"10.1515\/cclm-2020-1411","article-title":"Falsely markedly elevated 25-hydroxyvitamin D in patients with monoclonal gammopathies","volume":"59","author":"Hager","year":"2021","journal-title":"Clin Chem Lab Med"},{"key":"2026092302540753900_luag297-B5","doi-asserted-by":"crossref","first-page":"123","DOI":"10.1016\/j.cca.2016.04.013","article-title":"Hypercalcemia and elevated concentration of vitamin D: a case report too easy to be true","volume":"457","author":"Belaidi","year":"2016","journal-title":"Clin Chim Acta"},{"issue":"9","key":"2026092302540753900_luag297-B6","doi-asserted-by":"crossref","first-page":"1802","DOI":"10.1002\/ajh.27422","article-title":"Multiple myeloma: 2024 update on diagnosis, risk-stratification, and management","volume":"99","author":"Rajkumar","year":"2024","journal-title":"Am J Hematol"},{"issue":"8","key":"2026092302540753900_luag297-B7","doi-asserted-by":"crossref","first-page":"1734","DOI":"10.1515\/cclm-2026-0118","article-title":"M-protein interference in laboratory diagnostics: a comprehensive narrative review of mechanisms and management strategies","volume":"64","author":"Liang","year":"2026","journal-title":"Clin Chem Lab Med"},{"issue":"1","key":"2026092302540753900_luag297-B8","article-title":"Hematologists\/physicians need to be aware of pseudohypercalcemia in monoclonal gammopathy: lessons from a case report","volume":"2024","author":"Mennens","year":"2024","journal-title":"Case Rep Hematol"}],"container-title":["JCEM Case Reports"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/academic.oup.com\/jcemcr\/article-pdf\/4\/10\/luag297\/71332347\/luag297.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"syndication"},{"URL":"https:\/\/academic.oup.com\/jcemcr\/article-pdf\/4\/10\/luag297\/71332347\/luag297.pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,9,23]],"date-time":"2026-09-23T06:54:12Z","timestamp":1790146452000},"score":1,"resource":{"primary":{"URL":"https:\/\/academic.oup.com\/jcemcr\/article\/doi\/10.1210\/jcemcr\/luag297\/8831026"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,9,3]]},"references-count":8,"journal-issue":{"issue":"10","published-print":{"date-parts":[[2026,9,3]]}},"URL":"https:\/\/doi.org\/10.1210\/jcemcr\/luag297","relation":{},"ISSN":["2755-1520"],"issn-type":[{"value":"2755-1520","type":"electronic"}],"subject":[],"published-other":{"date-parts":[[2026,10]]},"published":{"date-parts":[[2026,9,3]]},"article-number":"luag297"}}