Update from Dr. David Clark: Von Willebrand Factor and COVID-19

Written by: David Clark, PhD, chair of the Coalition for Hemophilia B

Von Willebrand factor (VWF), a protein that plays several important roles in clotting, has become a subject of interest in COVID-19. Dr. Leonard Valentino, CEO of the National Hemophilia Foundation (NHF), published an update of the situation on the NHF website. VWF has at least two important roles in clotting.  First, it protects factor VIII in the bloodstream. Factor VIII, the protein deficient in people with hemophilia A, is a fairly fragile molecule that tends to degrade when it is by itself in the bloodstream. VWF binds to factor VIII and keeps it in good shape.

Excess VWF may play a role in the organ-damaging clotting that is seen in many COVID patients, but the story is still unfolding.

VWF also helps to bind a growing clot to the walls of blood vessels at the site of an injury. This keeps the clot where it is needed, but too much VWF can be dangerous and lead to too much clotting. Another protein called ADAMTS-13 keeps the amount of VWF under control. Researchers have discovered that excess VWF may play a role in the organ-damaging clotting that is seen in many COVID patients. It has been suggested that people with naturally lower levels of ADAMTS-13 may be at higher risk of developing severe COVID-19. Their lower levels of ADAMST-13 may allow the levels of VWF to get out of control.  An Italian study found that 5 of 6 severe COVID patients who had low levels of ADAMST-13 died.

The COVID-19 story is still unfolding, and this is just one discovery along the path. It still remains to be seen what the outcome will be. Research continues.