My Hands Turn Very Red..It Starts Right Above My Knuckles

My hands turn very red..It starts right above my knuckles and goes to my finger tips. My hands swell and it is painful. The redness above my knuckles is in a straight line from left to right. It looks like I have stuck my hand in a red liquid. The underside of my hands turn purple. I have been diagnosed with carpul tunnel and mild arthritis. My doctor just said that's weird and asked me what it was. She had no clue as she had never seen it before.