{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,24]],"date-time":"2026-10-24T02:05:56Z","timestamp":1792807556407,"version":"4.5.0"},"reference-count":21,"publisher":"BMJ","issue":"2","license":[{"start":{"date-parts":[[2026,2,18]],"date-time":"2026-02-18T00:00:00Z","timestamp":1771372800000},"content-version":"unspecified","delay-in-days":17,"URL":"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/"}],"content-domain":{"domain":["bmj.com"],"crossmark-restriction":true},"short-container-title":["BMJ Case Rep"],"accepted":{"date-parts":[[2026,2,2]]},"published-print":{"date-parts":[[2026,2]]},"abstract":"<jats:p>\n                    An elderly man underwent cardiac surgery with heparin anticoagulation; postoperatively, the platelet counts steadily fell, reaching 50\u00d710\n                    <jats:sup>9<\/jats:sup>\n                    \/L on postoperative day 5 (POD5), prompting testing for heparin-induced thrombocytopenia (HIT) antibodies; brain imaging showed parietal stroke. Screening immunoassay for HIT antibodies yielded a strong-positive result; the platelet activation test (serotonin-release assay) gave an atypical profile (strong serotonin release at 0, 0.1 and 0.3 U\/mL heparin with only partial inhibition by a platelet Fc receptor-blocking monoclonal antibody). Anticoagulation was changed to argatroban plus high-dose intravenous immunoglobulin. Persisting hypercoagulability prompted a switch to fondaparinux, with gradual platelet count recovery (155\u00d710\n                    <jats:sup>9<\/jats:sup>\n                    \/L, POD62); neurological abnormalities resolved. Laboratory evaluation confirmed HIT antibodies with heparin-independent platelet-activating properties, indicating autoimmune HIT (aHIT). Besides profound thrombocytopenia (platelet count nadir, 13\u00d710\u2079\/L), novel aspects of this case of aHIT include early postoperative onset (before POD5) resulting from preoperative heparin exposure and a unique laboratory aHIT antibody profile with partial resistance to Fc receptor blockade.\n                  <\/jats:p>","DOI":"10.1136\/bcr-2025-270108","type":"journal-article","created":{"date-parts":[[2026,2,19]],"date-time":"2026-02-19T05:15:20Z","timestamp":1771478120000},"page":"e270108","update-policy":"https:\/\/doi.org\/10.1136\/crossmarkpolicy","source":"Crossref","is-referenced-by-count":2,"title":["Autoimmune heparin-induced thrombocytopenia following cardiac surgery"],"prefix":"10.1136","volume":"19","author":[{"given":"Rosanne","family":"St Bernard","sequence":"first","affiliation":[{"name":"Department of Medicine, Grand River Hospital, Kitchener, Ontario, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ishac","family":"Nazy","sequence":"additional","affiliation":[{"name":"Department of Medicine, McMaster University, Hamilton, Ontario, Canada"},{"name":"Department of Biochemistry and Biomedical Sciences, McMaster University Faculty of Health Sciences, Hamilton, Ontario, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8046-7588","authenticated-orcid":false,"given":"Theodore Earl","family":"Warkentin","sequence":"additional","affiliation":[{"name":"Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, 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