George, My daughter and I seem to have a tendency to bruise easily. She just got a big bruise the other day from a surfing accident and that episode started the conversation of why we bruise. I wonder if it could be a genetic possibility. We also are both blood type O and “23 and Me” says I have a mutation to bleed easier so I would not need as much Coumadin if I ever was on that medication.
Thank you for your message, and I suggest you start with the most common inherited bleeding disorder, low von Willebrand factor, or possibly von Willebrand disease. The usual first-line phenotypic test series includes VWF:ag, VWF:activity, and factor VIII activity assay. There are three VWF:activity assays, the “vintage” VWF:RCo, and the current and more reliable VWF:GP1bR or VWF:GP1bM. Most FVIII activity assays are clot-based, but labs are moving to chromogenics, which are more reliable.
It is unlikely you and your daughter would classify as having von Willebrand disease, defined as a VWF level <30 U/dL, but given you are both blood group O, you could have “low VWF,” with a level between 30 and 50 U/dL. In this case, as indicated in your email, you will want to avoid any of the therapeutics that raise the bleeding risk.
Your providers may wish to escalate to genetic testing and would want to include any other first-degree relatives. If the first-line testing is negative, the next step would be platelet aggregometry, which would reveal a possible platelet abnormality, which would be much less common than low VWF.
Thank you for your question, and I invite comments.