Common cold linked to rare and fatal blood-clotting disorder

Blood clot made of red blood cells, platelets and fibrin protein strands. Thrombus, 3D illustration (Getty Images/iStockphoto)
Blood clot made of red blood cells, platelets and fibrin protein strands. Thrombus, 3D illustration (Getty Images/iStockphoto)

A potentially fatal disorder which causes blood clotting has been linked to a common cold, according to researchers from the University of North Carolina School of Medicine.

The team found a connection between adenovirus – a group of viruses that can cause mild to severe infection in the body – and a rare blood clotting disorder.

This is the first time that the common respiratory virus has been reported to be associated with blood clots and severe thrombocytopenia.

Platelets, often termed thrombocytes are crucial in forming blood clots when people get injuries.

Viral infections, autoimmune diseases and other conditions can cause platelet levels to drop throughout the body. This is known as thrombocytopenia.

“This adenovirus-associated disorder is now one of four recognized anti-PF4 disorders,” said Dr Stephen Moll, professor of medicine in the Department of Medicine’s Division of Hematology, in a university release.

“We hope that our findings will lead to earlier diagnosis, appropriate and optimized treatment, and better outcomes in patients who develop this life-threatening disorder.”

The latest findings, published in the New England Journal of Medicine, provide details on the virus and its role in causing an anti-platelet factor 4 disorder.

The discovery also opens new avenues of research to understand why and how this condition occurs.

In anti-PF4 disorders, a person’s immune system creates antibodies against PF4, a protein that is released by platelets. Antibodies are proteins that help fight off harmful illnesses.

However, when an antibody forms against PF4 and binds to it, activation, and rapid removal of platelets in the bloodstream can be triggered and lead to blood clotting and low platelets.

Occasionally, a patient’s exposure to heparin called heparin-induced thrombocytopenia (HIT), triggers the formation of anti-PF4 antibodies. Sometimes, it occurs as an autoimmune condition without any previous heparin exposure, which is called spontaneous HIT.

In the last three years, a small number of cases of thrombocytopenia have been linked to specific Covid-19 vaccines, distinct from those produced by Moderna and Pfizer. This condition is termed vaccine-induced immune thrombotic thrombocytopenia (VITT).

To understand this better, researchers looked into a five-year-old boy who was previously diagnosed with an adenovirus infection and was hospitalized with a severe blood clot in his brain and significantly reduced platelet levels.

“The intensive care unit physicians, the neuro-intensivist, and hematology group were working around the clock to determine next steps in the care for this young boy,” said Dr Jacquelyn Baskin-Miller.

“He wasn’t responding to therapy and was progressing quickly. We had questioned whether it could have been linked to his adenovirus considering the vaccine data, but there was nothing in the literature at that time to suggest it.”

The results showed that the boy had an antibody typically associated with HIT. There was a similar case reported about another patient with an adenovirus infection which led to more testing.

The tests showed that the patient’s antibodies were targeting the same protein as HIT antibodies, which concluded that they had a variant of HIT linked to the adenovirus infection.

Researchers are now left with many unanswered questions on how common this disorder is and if it can be caused by other viruses.

“How common is the disorder? What degree of thrombocytopenia raises the threshold to test for anti-PF4 antibodies? And then finally, how do we best treat these patients to optimize the chance that they will survive such a potentially deadly disease?” Dr Moll asked.

Blood clot symptoms you need to know about

Although blood clots protect you from bleeding too much if you have an injury or surgery - there could be other reasons for the disorder, which can be harmful.

According to the Cleveland Clinic, blood clots can cause potentially life-threatening symptoms and those most at risk include:

• People aged 65 years and over have an increased risk of blood clots.

• Women who are pregnant.

• People diagnosed with cancer.

• People diagnosed with Obesity.

• People who may be taking birth control pills or having hormone therapy.

• People who smoke.

What is Adenovirus?

Adenoviruses are a group of viruses that can affect different parts of the body. This is solely dependent on the type.

The US Centers for Disease Control and Prevention website has said the range of illnesses associated with adenoviruses include common cold or flu-like symptoms, such as a fever and sore throat.

Acute bronchitis, pneumonia, conjunctivitis and acute gastroenteritis – including vomiting and diarrhoea – can also result from infection.

Bladder inflammation or infection and neurological disease are less common but are also listed as symptoms.