Researchers at McMaster University have made a groundbreaking discovery in the field of hematology, providing an explanation for spontaneous and unusual bleeding episodes that continue to occur despite treatment with full-dose blood thinners.

The discovery, published February 12, 2025 in The New England Journal of Medicine is expected to impact the way doctors test and treat patients with unusual or recurring blood clotting, with the potential to improve patient outcomes.

The researchers found that this new blood clotting disorder shares certain similarities with vaccine-induced immune thrombocytopenia and thrombosis (VITT)—a rare but aggressive clotting disorder caused by certain discontinued CoVID-19 vaccines.

Research shows that certain patients can develop severe blood clotting due to antibodies very similar to those that cause Vitt, even in the absence of known triggers for such antibodies such as blood thinners (heparin) or previous vaccination.

The newly identified disorder was named Vitt-like monoclonal gammopathy of thrombotic significance (MGTs).

Our study underscores the importance of recognizing and diagnosing this new blood-cost disorder.” Theodore (TED) Warkentin, co-first author and corresponding author of the study and Professor Emeritus, Department of Pathology and Molecular Medicine, McMaster University

“Understanding how to diagnose Vitt-like MGTs will help us develop more effective treatment strategies beyond traditional anticoagulation,” said Warkentin, a hematologist at Hamilton Health Sciences’ Hamilton General Hospital.

Specialized testing was performed at the McMaster Platelet Immunology Laboratory in the Michael G. DeGroote Centre for Transfusion Research, the only laboratory in Canada with the full repertoire of tests needed to characterize the Vitt-like antibodies that target the PF4 protein. The researchers conducted a detailed analysis of cases that had unusual blood clots despite patients being on full-dose blood thinners, focusing on patients with unexplained Vitt-like antibodies that had been detectable for a year or more.

The analyses identified the presence of M (monoclonal) proteins (which typically indicate plasma cell disorders) along with persistent Vitt-like reactivities for at least 12 months (which for most anti-PF4 is an ongoing pathological process rather than a short-term abnormality.

The study involved a multinational collaboration with data from five patients treated at facilities in Canada, New Zealand, France, Spain and Germany.

Collaborator Jing Jing Wang of Flinders University in Australia played a crucial role in providing evidence for each patient that the M proteins are the pathological Vitt-like antibodies. Collaborator Andreas Greinacher of Greifswald University in Germany helped identify similar cases in his anti-PF4 reference laboratory.

“The results of this study underscore our ability to use basic molecular and biochemical science to unravel disease mechanisms.” Degroote Center for Transfusion Medicine.

One notable observation was that . The existence of this novel bleeding disorder has important implications for how healthcare providers evaluate patients who develop unusual or difficult-to-treat blood clots in the future.

Journal Reference:

Wang, JJ, et al. (2025). Vitt-like monoclonal gammopathy of thrombotic significance. New England Journal of Medicine . doi.org/10.1056/nejmoa2415930 .