New York, Aug 11 (IANS): Researchers have for the first time found an association with adenovirus infection, the common respiratory virus that causes mild cold-and flu-like symptoms, with blood clots and severe thrombocytopenia -- low platelet levels in the body.
The study, published in the New England Journal of Medicine presents case reports of two patients shedding new light on the virus and its role in causing an anti-platelet factor 4 (PF4) disorder.
"This adenovirus-associated disorder is now one of four recognised anti-PF4 disorders," said Stephan Moll, Professor of medicine at the University of North Carolina in the US.
"We hope that our findings will lead to earlier diagnosis, appropriate and optimised treatment, and better outcomes in patients who develop this life-threatening disorder," Moll added.
In anti-PF4 disorders, the person's immune system makes antibodies against platelet factor-4, a protein that is released by platelets.
When an antibody forms against PF4 and binds to it, this can trigger the activation and rapid removal of platelets in the bloodstream, leading to blood clotting and low platelets, respectively.
Sometimes, the formation of anti-PF4 antibodies is triggered by a patient's exposure to heparin, called heparin-induced thrombocytopenia (HIT), and sometimes it occurs as an autoimmune condition without heparin exposure, which is referred to as "spontaneous HIT".
In the last three years, thrombocytopenia has been shown to rarely occur after injection with Covid -19 vaccines that are made with inactivated pieces of an adeno-viral vector.
These vaccines are different from the ones made in the US, such as those by Moderna and Pfizer. The condition is referred to as (VITT).
In the study, the team reported the case of a 5-year-old boy who had been diagnosed as an outpatient with adenovirus infection and had to be admitted to the hospital with an aggressive blood clot forming in his brain (called cerebral sinus vein thrombosis) and severe thrombocytopenia.
Doctors determined that he hadn't been exposed to heparin or the adeno-vector Covid-19 vaccination -- the classical triggers for HIT and VITT.
As the boy "wasn't responding to therapy and was progressing quickly" the team tested for the HIT platelet activating antibody, which came back positive.
Separately, Alison L. Raybould, a haematologist-oncologist in Virginia, a previous trainee from UNC was seeing a patient who had multiple blood clots, a stroke and heart attack, arm and leg deep-vein thrombosis (DVT), and severe thrombocytopenia.
The patient had not been exposed to heparin or vaccines.
However, this patient's severe illness had also started with viral symptoms of cough and fever, and she had tested positive for adenoviral infection.
Testing for an anti-PF4 antibody also turned out to be positive. Further lab tests confirmed that the antibodies were targeting platelet factor 4, much like the HIT antibodies.
Surprisingly, the antibody resembled that of the VITT and bound to PF4 in the same region as VITT antibodies do. They concluded that both the patients had "spontaneous HIT" or a VITT-like disorder, associated with an adenovirus infection.
More studies are necessary to understand questions about the prevalence of the new anti-PF4 disorder, whether the condition can be caused by other viruses, and why this condition doesn't occur with every infection with adenovirus, the team said.
They also wonder what preventative or treatment measures can be made to help patients who develop the new, potentially deadly anti-PF4 disorder.