Can Thrombosis And High Protein Level Cause Stiff Person Syndrome?

My 50 yr old husband has high levels of Factor Vlll (291) and Factor V. in his blood. He had DVT four times and pulmonary embolisms. He is on warafan. Would there be any link in this and his whole body starting to stiffen up in his muscles and bones? He is in major pain all the time and the drs can;t seem to find anything wrong. He has been tested for Stiff person syndrome...but the test came back negative. However the neurologist still won't rule that out. We just want to know why he is always in crippling pain. Might it have anything to do with the proteins and the liver and the Factor VIII?