And all this time I thought it was do to a lack of oxygen.
One day when working in the ED one of my partners came to me with a “great case”. A 17 year old came in with cyanotic (blue) hands. He wanted my opinion. The girl was healthy, not short of breath and had a completely normal exam except for these weird blue hands. He had asked her every question he could think of, including some very exotic poisoning scenarios and was stumped. I went in to take a look and sure enough she had these very cyanotic hands with very blue nail beds. At this point my partner was about to order a CT of her chest to rule out a pulmonary embolism, when I noticed the blue looked a little different from the usual. I grabbed an alcohol wipe and low and behold the blue, came off. Turns out she had a new pair of jeans and had had her hands in the pockets a lot. On closer inspection her butt and legs were also faintly blue....
took my partner a while to get over that one.