What Does This MRI Report Indicate?

My son legs turn blue only when he stands still. After a couple min they will then stray growing red/white blotches. Upon moving they immediately return to normal. They also itch painfully. It will also happen to his arms if they hang in an unnatural position and his head if it is upside down. He has seen more than 40 doctors who have come to no conclusions. He has had biopsies, blood tests, nerve tests, sweat tests, tilt table tests and many many more. The only irregularities they find are in his MRI they said his blood vessels are clustered . The neurologist said this is not an issue though. Now my 7 year old daughter has started turning blue also. She is not itchy yet tho. My other two children have no symptoms.