Hi. I happened to look at this for the first time today and search on "Pulmonary Embolism" so I realize my comments are being added to posts that are 1-2 years old, but worth a shot to help...

In addition to getting tested for Factor V, also have your hematologist test your Protein S - both function and activity (not sure if those are the right terms but there are two separate blood tests).

In 2014 at age 42 I stood up at work one day and doubled over in pain in chest; within minutes every breath was terribly painful as was bending over. Turns out I had a DVT behind in my right knee and a massive bilateral PE and was hospitalized for almost a week. Well through that process it was determined that I have a Protein S deficiency, which we also figured out was genetic on my mother's side of the family.

I then had a run (about 1 year) on Coumadin and Lovenox (when flying for work) before I reverted to baby aspirin.

Then in 2020, I had another much smaller PE and no DVT was ever found. Since then I have been on Xarelto (20mg daily at first, down to 10mg after about 2 years) and I expect to be on it for life.

So far so good, nothing since, but I happened upon this today because a difficult to diagnose case of pneumonia (lungs sounded good multiple times to doc listening and a clear chest x-ray) led me to another CT scan with dye to rule out a PE. Thankfully no PE but discovered the pneumonia.

Long way of saying, Protein S is another one to get checked out as it relates to clotting disorders (as is Protein C I think).