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Volume 26, Number 10—October 2020

Pulmonary Embolism and Increased Levels of D-Dimer in Patients with Coronavirus Disease

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To the Editor: We read with great interest the recent report by Griffin et. al. (1). Griffin et al. reported on 3 patients in whom pulmonary embolism developed after the cytokine storm phase of coronavirus disease (COVID-19); the patients were treated with steroids and tocilizumab. We have observed a transient elevation of D-dimer in patients after tocilizumab treatment, which leads to an interesting discussion about whether the pulmonary embolism observed in these COVID-19 patients was due to a persistent hypercoagulable state in the late phase of the disease or a transient one related to tocilizumab.

Tocilizumab is a humanized antihuman interleukin-6 (IL-6) receptor monoclonal antibody that inhibits IL-6 signaling. Use of tocilizumab in the COVID-19 pandemic has been growing. It presumptively targets the cytokine storm phase of the disease by inhibiting the IL-6 pathway (2). However, IL-6 has a multifaceted role in venous thromboembolism, and Zhang et al. has reported that upregulation of IL-6 as the result of aberrant downregulation of miR-338-5p may lead to venous thromboembolism (3).

Conversely, using a rat model, Nosaka et al. demonstrated the importance of iIL-6 in resolving thrombi through macrophage recruitment and proteolytic enzymes induction (4). The absence of IL-6, in fact, leads to the thrombus growing (4). Moreover, tocilizumab has been reported to decrease factor XIII, chemerin, and plasminogen activator inhibitor levels (5). Factor XIII is involved in fibrin stabilization; blocking this factor may lead to fibrin clot instability, causing microthrombi to dislodge, increasing the likelihood of thrombophilia.

The association of tocilizumab with thrombosis is not clearly understood. However, the potential for adverse effects that we describe may warrant a short period of therapeutic anticoagulation before and after administering tocilizumab. The hypercoagulable state reported in the findings by Griffin et. al. may represent a side effect of tocilizumab rather than being a condition secondary to COVID-19, or it could result from a combination of both.


Kok Hoe ChanComments to Author , Jihad Slim, and Hamid S. Shaaban
Author affiliations: St. Michael’s Medical Center, Newark, New Jersey, USA



  1. Griffin  DO, Jensen  A, Khan  M, Chin  J, Chin  K, Saad  J, et al. Pulmonary embolism and increased levels of D-dimer in patients with coronavirus disease. Emerg Infect Dis. 2020;26. DOIPubMedGoogle Scholar
  2. Zhang  C, Wu  Z, Li  JW, Zhao  H, Wang  GQ. The cytokine release syndrome (CRS) of severe COVID-19 and Interleukin-6 receptor (IL-6R) antagonist tocilizumab may be the key to reduce the mortality. Int J Antimicrob Agents. 2020;55:105954. DOIGoogle Scholar
  3. Zhang  Y, Zhang  Z, Wei  R, Miao  X, Sun  S, Liang  G, et al. IL (interleukin)-6 contributes to deep vein thrombosis and is negatively regulated by miR-338-5p. Arterioscler Thromb Vasc Biol. 2020;40:32334. DOIPubMedGoogle Scholar
  4. Nosaka  M, Ishida  Y, Kimura  A, Kuninaka  Y, Taruya  A, Ozaki  M, et al. Crucial involvement of IL-6 in thrombus resolution in mice via macrophage recruitment and the induction of proteolytic enzymes. Front Immunol. 2020;10:3150. DOIPubMedGoogle Scholar
  5. Jewell  P, Ansorge  O, Kuker  W, Irani  SR, Zamboni  G. Tocilizumab-associated multifocal cerebral thrombotic microangiopathy. Neurol Clin Pract. 2016;6:e246. DOIPubMedGoogle Scholar


Cite This Article

DOI: 10.3201/eid2610.202127

Original Publication Date: September 17, 2020

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Kok Hoe Chan, Saint Michael’s Medical Center, 111 Central Ave, Newark, NJ 07101, USA

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Page created: May 26, 2020
Page updated: September 17, 2020
Page reviewed: September 17, 2020
The conclusions, findings, and opinions expressed by authors contributing to this journal do not necessarily reflect the official position of the U.S. Department of Health and Human Services, the Public Health Service, the Centers for Disease Control and Prevention, or the authors' affiliated institutions. Use of trade names is for identification only and does not imply endorsement by any of the groups named above.