Andrew Shih, MD, FRCPC, DRCPSC, BSc, Vancouver General Hospital, Department of Pathology, JPP1, room 1553, 855 West 12th Avenue, Vancouver, B. C. V5Z 1M9, Canada, Tel.: +1 604 875 4111 Ext. 61109, E-mail:
Thromb Haemost. 2017 Oct 5;117(10):1868-1874. doi: 10.1160/TH17-03-0212. Epub 2017 Aug 24.
One of the standard distinctions between type 1 (non-immune) and type 2 (immune-mediated) heparin-induced thrombocytopenia (HIT) is the transience of thrombocytopenia: type 1 HIT is viewed as early-onset and transient thrombocytopenia, with platelet count recovery despite continuing heparin administration. In contrast, type 2 HIT is viewed as later-onset (i. e., 5 days or later) thrombocytopenia in which it is generally believed that platelet count recovery will not occur unless heparin is discontinued. However, older reports of type 2 HIT sometimes did include the unexpected observation that platelet counts could recover despite continued heparin administration, although without information provided regarding changes in HIT antibody levels in association with platelet count recovery. In recent years, some reports of type 2 HIT have confirmed the observation that platelet count recovery can occur despite continuing heparin administration, with serological evidence of waning levels of HIT antibodies ("seroreversion"). We now report two additional patient cases of type 2 HIT with platelet count recovery despite ongoing therapeutic-dose (1 case) or prophylactic-dose (1 case) heparin administration, in which we demonstrate concomitant waning of HIT antibody levels. We further review the literature describing this phenomenon of HIT antibody seroreversion and platelet count recovery despite continuing heparin administration. Our observations add to the concept that HIT represents a remarkably transient immune response, including sometimes even when heparin is continued.
1 型（非免疫）和 2 型（免疫介导）肝素诱导的血小板减少症（HIT）的标准区别之一是血小板减少症的短暂性：1 型 HIT 被视为早期和短暂性血小板减少症，尽管继续给予肝素治疗，但血小板计数恢复。相比之下，2 型 HIT 被视为后期（即 5 天或更晚）血小板减少症，通常认为除非停止使用肝素，否则血小板计数不会恢复。然而，关于 2 型 HIT 的旧报告有时确实包括出乎意料的观察结果，即尽管继续给予肝素治疗，但血小板计数仍可恢复，尽管没有提供与血小板计数恢复相关的 HIT 抗体水平变化的信息。近年来，一些关于 2 型 HIT 的报告证实了尽管继续给予肝素治疗，血小板计数仍可恢复的观察结果，并伴有 HIT 抗体水平下降的血清学证据（“血清学逆转”）。我们现在报告另外两例尽管持续给予治疗剂量（1 例）或预防剂量（1 例）肝素，但血小板计数仍恢复的 2 型 HIT 患者病例，其中我们证明了 HIT 抗体水平同时下降。我们进一步回顾了描述这种 HIT 抗体血清学逆转和尽管继续给予肝素治疗但血小板计数恢复现象的文献。我们的观察结果增加了 HIT 代表一种非常短暂的免疫反应的概念，包括有时即使肝素继续使用。
