. >> pele with pv, like debra trently d merle wertman, suffer from an overproduction of red blood cells. >> so the blood gets very thick, and it can cause, you know, blockages to smaller blood vessels that feed vital organs of our body. tissue death can occur anywhere in the body. it can occur in their brain, it can occur in their toe, it can occur in their liver. we've seen patients where they've developed infarctions to their feet, where they've had to have toes amputated. they have infarctions to their liver. they can have an infarction to their heart, much like a heart attack. >> the way it works on you, you're so exhausted and tired, you have chronic pain everywhere. i have chronic fatigue. headaches, terrible. it affects your vision. i'll just wake up and have pains in my legs and my hands and my feet. it's vascul, so it goes through every part, every vein on your body, you're having a lot of pain, every direction. you don't know where to put yourself. >> for merle, who has been a sports fanatic all his life, pv has really changed his once active lifestyle. >> these are--some of t