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血小板増多

著者: 樋口敬和 獨協医科大学埼玉医療センター 輸血部

監修: 神田善伸 自治医科大学附属病院 血液科

著者校正/監修レビュー済:2021/08/04
参考ガイドライン:
  1. Guideline for investigation and management of adults and children presenting with a thrombocytosis.
  1. WHO classification of tumours of haematopoietic and lymphoid tissues 2017.
患者向け説明資料

概要・推奨   

  1. 二次性(反応性)血小板増多症が圧倒的に多く、血小板増多をみたらまず血小板増多をきたす基礎疾患の存在を検討する。
  1. 反応性の血小板増多であっても100万/μlを超える著明な血小板増多を来すことがあるので、著明な血小板増多でも血小板増多の原因となる病態がないか検討する。
  1. 二次性(反応性)血小板増多症をきたす原因がなければ、一次性(クローン性)血小板増多症を考える。
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薬剤監修について:
オーダー内の薬剤用量は日本医科大学付属病院 薬剤部 部長 伊勢雄也 以下、林太祐、渡邉裕次、井ノ口岳洋、梅田将光による疑義照会のプロセスを実施、疑義照会の対象については著者の方による再確認を実施しております。
※薬剤中分類、用法、同効薬、診療報酬は、エルゼビアが独自に作成した薬剤情報であり、
著者により作成された情報ではありません。
尚、用法は添付文書より、同効薬は、薬剤師監修のもとで作成しております。
※薬剤情報の(適外/適内/⽤量内/⽤量外/㊜)等の表記は、エルゼビアジャパン編集部によって記載日時にレセプトチェックソフトなどで確認し作成しております。ただし、これらの記載は、実際の保険適用の査定において保険適用及び保険適用外と判断されることを保証するものではありません。また、検査薬、輸液、血液製剤、全身麻酔薬、抗癌剤等の薬剤は保険適用の記載の一部を割愛させていただいています。
(詳細はこちらを参照)
著者のCOI(Conflicts of Interest)開示:
樋口敬和 : 特に申告事項無し[2021年]
監修:神田善伸 : 未申告[2021年]

改訂のポイント:
  1. 定期レビューを行い、一部改訂した。

病態・疫学・診察

疫学情報・病態・注意事項  
  1. 通常、血小板数45万/μl以上を血小板増多とする。
  1. クローン性(腫瘍性)巨核球により血小板産生が自律的に亢進している一次性(クローン性)血小板増多症と、他の基礎疾患により血小板産生が亢進する二次性(反応性)血小板増多症に分類される。
  1. 小型赤血球(重症熱傷時)、クリオグロブリン、破砕赤血球などを自動血球計測機が血小板としてカウントすることにより偽性血小板増多症をきたすことがあるが、これらは末梢血塗抹標本の鏡検により鑑別される。
  1. 二次性血小板増多症の頻度が圧倒的に高く(90~95%)、血小板増多をみたらまず血小板増多をきたす基礎疾患について検討することが重要である。
  1. 二次性血小板増多症では基礎疾患の存在が明らかな場合が多いが、基礎疾患が診断できない場合に悪性腫瘍などの病態が潜んでいることもあり注意が必要である。
  1. 二次性血小板増多症では血小板数が100万/μlを超えることは少ないが、ときに100万/μlを超える著明な血小板増多を来すこともあり、血小板数だけでは両者を鑑別できない。
  1. 一次性血小板増多症では、血栓症のリスクが上昇する。
  1. 一次性血小板増多症で血小板数が100万/μlを超える著明な血小板増多をきたしている場合には、後天性von Willebrand症候群を合併して出血(主に皮下や粘膜出血)のリスクが上昇することがある。
  1. 二次性血小板増多症では、他の合併症がなければ血栓症のリスクは上昇しない。しかし、基礎疾患として悪性腫瘍などが存在したり、他のリスク因子が存在する場合は、静脈血栓症のリスクが上昇する。
  1. 1回だけの血液検査で「血小板増多症」と確定しないで、再検して血小板が持続的に増加していることを確認する。
 
問診・診察のポイント  
 
問診:
  1. 以前の血小板のデータがあるか聴取して、あれば入手する。

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文献 

著者: C R Santhosh-Kumar, M D Yohannan, K E Higgy, S A al-Mashhadani
雑誌名: J Intern Med. 1991 Jun;229(6):493-5.
Abstract/Text A total of 777 patients with thrombocytosis, defined as a platelet count of greater than 500 x 10(9)l-1, seen in a University hospital over a 1-year period, were studied prospectively for aetiology. The most frequent causes of thrombocytosis were infection (21.9%), rebound thrombocytosis (19.4%), tissue damage (17.9%), chronic inflammatory disorders (13.1%) and malignancy (5.9%). Thrombocytosis associated with multiple causative factors, occurring simultaneously, was seen in 6.1% of cases. Thrombocytosis of greater than or equal to 1 million x 10(9)l-1 was found most frequently in patients with multiple aetiological factors occurring at the same time, in myeloproliferative disorders, or in postsplenectomy patients.

PMID 2045755  J Intern Med. 1991 Jun;229(6):493-5.
著者: Kazuo Dan, Takashi Yamada, Yukihiko Kimura, Noriko Usui, Shinichirou Okamoto, Takashi Sugihara, Kazue Takai, Michihiko Masuda, Mayumi Mori, Japanese Elderly Leukemia and Lymphoma Study Group
雑誌名: Int J Hematol. 2006 Jun;83(5):443-9. doi: 10.1532/IJH97.06009.
Abstract/Text We conducted the first nationwide survey to clarify the clinical features, treatment methods, and prognoses for polycythemia vera (PV) and essential thrombocythemia (ET). A 1-page questionnaire was mailed to members of the Japanese Elderly Leukemia and Lymphoma Study Group (JELLSG). Surveys on 647 patients (PV, 266 patients; ET, 381 patients) were returned and analyzed. Thrombotic events at diagnosis and during follow-up occurred at rates of 15.4% and 8.5%, respectively, in PV cases and 17.6% and 8.7% in ET cases. Splenomegaly was observed in only 28.8% of PV patients and 10.8% of ET patients. The leukocyte alkaline phosphatase score was elevated in only 46.2% of PV patients. The incidences of abnormal karyotypes were less than 10% in both PV and ET cases. The rates of transformation to myelofibrosis were 2.6% in both PV and ET cases, and acute leukemia was noted in 1.1% of PV patients and 2.9% of ET patients. Prognostic factors were thrombotic history for PV and thrombotic history and age (>or=60 years) for ET. The present study clearly demonstrated clinical differences between Japanese and Western patients for PV and ET. Concerning the treatment of PV and ET, the study revealed considerable variation among Japanese hematologists. These results suggest the necessity of developing treatment guidelines according to risk stratification that are suitable for Japanese PV and ET patients.

PMID 16787877  Int J Hematol. 2006 Jun;83(5):443-9. doi: 10.1532/IJH97・・・
著者: Claire N Harrison, David Bareford, Nauman Butt, Peter Campbell, Eibhlean Conneally, Mark Drummond, Wendy Erber, Tamara Everington, Anthony R Green, Georgina W Hall, Beverley J Hunt, Christopher A Ludlam, Richard Murrin, Catherine Nelson-Piercy, Deepti H Radia, John T Reilly, Jon Van der Walt, Bridget Wilkins, Mary F McMullin, British Committee for Standards in Haematology
雑誌名: Br J Haematol. 2010 May;149(3):352-75. doi: 10.1111/j.1365-2141.2010.08122.x. Epub 2010 Mar 15.
Abstract/Text
PMID 20331456  Br J Haematol. 2010 May;149(3):352-75. doi: 10.1111/j.1・・・
著者: A Tefferi, T C Ho, G J Ahmann, J A Katzmann, P R Greipp
雑誌名: Am J Med. 1994 Oct;97(4):374-8.
Abstract/Text PURPOSE: Evaluate the discriminatory value of plasma interleukin-6 or C-reactive protein levels in clonal thrombocytosis compared with those in reactive thrombocytosis.
PATIENTS AND METHODS: A comparative analysis of quantitatively measured laboratory values in a prospectively studied group of consecutive patients. The setting was a tertiary referral center consisting of two hospitals and an outpatient clinic. Plasma interleukin-6 and C-reactive protein levels were measured in 91 consecutive patients with thrombocytosis (platelet count > or = 600 x 10(9)/L). The cause of thrombocytosis was determined by reviewing the medical histories and follow-up data without knowledge of the corresponding laboratory values. Sixty-four patients had reactive thrombocytosis, 20 had clonal thrombocytosis, and 7 had clonal thrombocytosis plus reactive thrombocytosis. Plasma interleukin-6 was measured by an enzyme-linked immunosorbent assay, and C-reactive protein was measured with rate immunonephelometry.
RESULTS: Interleukin-6 levels were undetectable in all the patients with clonal thrombocytosis, whereas they were increased in 60% of the patients with reactive thrombocytosis or clonal thrombocytosis plus reactive thrombocytosis. There was a correlation between interleukin-6 and C-reactive protein levels (r = .6), and the median and range values of both levels differed significantly between the clonal thrombocytosis group and the other two groups (P < 0.0001). In 81% of the patients with reactive thrombocytosis, levels of either interleukin-6 or C-reactive protein were elevated. There was no correlation between interleukin-6 and C-reactive protein levels and the platelet count.
CONCLUSIONS: An elevated interleukin-6 level is rare in uncomplicated clonal thrombocytosis and suggests reactive thrombocytosis. However, an isolated normal value has little discriminatory value. Measurement of C-reactive protein level may be used as a less expensive surrogate for measurement of interleukin-6. Repeatedly low levels of both interleukin-6 and C-reactive protein are most consistent with clonal thrombocytosis.

PMID 7942941  Am J Med. 1994 Oct;97(4):374-8.
著者: M Griesshammer, M Bangerter, T Sauer, R Wennauer, L Bergmann, H Heimpel
雑誌名: J Intern Med. 1999 Mar;245(3):295-300.
Abstract/Text OBJECTIVE: To determine the aetiology and clinical significance of an elevated platelet count (thrombocytosis) in a large cohort of patients.
DESIGN: A retrospective review of the medical records was performed on all patients, who had at least one platelet count > or = 500 x 10(9) L-1.
SETTING: Departments of Medicine and Surgery, University of Ulm, Germany.
SUBJECTS: A total of 732 patients with thrombocytosis.
MAIN OUTCOME MEASURES: Classification of thrombocytosis and thromboembolic complications, and evaluation of laboratory parameters distinguishing between primary and secondary thrombocytosis.
RESULTS: Of the total of 732 patients, 89 (12.3%) had primary and 643 (87.7%) had secondary thrombocytosis. Essential thrombocythaemia was observed in 40 of 89 patients (45%) with primary thrombocytosis. The most frequent causes of secondary thrombocytosis were tissue damage (42%), infection (24%), malignancy (13%) and chronic inflammation (10%). Primary thrombocytosis was significantly associated with a higher platelet count and an increased incidence of both arterial and venous thromboembolic complications. In secondary thrombocytosis, thromboembolic events were restricted to the venous system and occurred only in the presence of other risk factors. Mean values of leucocyte count, haematocrit, erythrocyte sedimentation rate, fibrinogen, serum potassium and lactate dehydrogenase were significantly different in primary and secondary thrombocytosis.
CONCLUSIONS: The finding of an elevated platelet count on routine blood examination has diagnostic, prognostic and therapeutic implications. It is of clinical importance to distinguish between primary and secondary thrombocytosis, as thrombotic complications occur more frequently in primary thrombocytosis. Unless additional risk factors are present, secondary thrombocytosis is not associated with a significant risk for thromboembolic events.

PMID 10205592  J Intern Med. 1999 Mar;245(3):295-300.
著者: P J Stohlawetz, L Dzirlo, N Hergovich, E Lackner, C Mensik, H G Eichler, E Kabrna, K Geissler, B Jilma
雑誌名: Blood. 2000 May 1;95(9):2983-9.
Abstract/Text A recent study in dogs suggested that erythropoietin (EPO) not only promotes the synthesis of increased numbers of reticulated platelets but that these newly produced platelets are hyperreactive compared with controls. Because of the increasing use of EPO in the perioperative setting, we characterized the effects of EPO on platelet reactivity in healthy human volunteers. In a randomized, controlled trial, we studied the effects of EPO on platelet reactivity, thrombopoiesis, and endothelial activation in circumstances similar to those of autologous blood donation. Thirty healthy male volunteers received placebo or EPO (100 or 500 U/kg of body weight given intravenously) three times a week for 2 weeks and underwent phlebotomy on days 8 and 15. Thrombin receptor-activating peptide induced expression of P-selectin, and CD63 increased 2- to 3-fold during EPO treatment. The enhanced platelet reactivity was also reflected by a 50% increase in soluble P-selectin in plasma. Plasma E-selectin levels increased in a dose-dependent fashion by more than 100% during EPO treatment, indicating substantial activation of endothelial cells. A 10% to 20% increase in platelet counts was observed in both EPO groups on day 5. In the placebo group, platelets increased only several days after the first phlebotomy. The increase in platelet counts was not reflected by changes in the amounts of reticulated platelets or circulating progenitor cells. In summary, we found that EPO markedly enhances endothelial activation and platelet reactivity, which may adversely affect patients at cardiovascular risk. However, the increased platelet reactivity could be exploited in patients with platelet dysfunction. (Blood. 2000;95:2983-2989)

PMID 10779449  Blood. 2000 May 1;95(9):2983-9.
著者: D H Buss, A W Cashell, M L O'Connor, F Richards, L D Case
雑誌名: Am J Med. 1994 Mar;96(3):247-53.
Abstract/Text PURPOSE: To determine the etiology and to evaluate the clinical consequences of an extremely elevated platelet count.
PATIENTS AND METHODS: A review of the medical records was performed on all patients encountered during a 5 1/2-year period who had at least one platelet count of 1,000 x 10(9)/L or greater.
RESULTS: Of the total of 280 patients with extreme thrombocytosis (EXT), 231 (82%) had reactive thrombocytosis (RT), 38 (14%) had a myeloproliferative disorder (MPD), and 11 (4%) had cases of uncertain etiology. RT was more common than MPD in all age groups except those in the eighth decade and older. Symptoms of bleeding and/or vaso-occlusive phenomena were noted in association with EXT in 21 (56%) of the MPD patients but in only 10 (4%) of the RT patients. Treatment to lower the platelet count and/or inhibit platelet function was employed in 36 MPD patients and 23 RT patients. Eight patients with MPD and 34 with RT are known to have died, but no patient in either group is known to have died of a thrombotic or bleeding event when the platelet count was greater than or equal to 1,000 x 10(9)/L.
CONCLUSIONS: Platelet counts greater than or equal to 1,000 x 10(9)/L should not be considered rare events in the general, acute-care hospital population, and usually represent a reactive phenomenon.

PMID 8154513  Am J Med. 1994 Mar;96(3):247-53.

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