The Blue People of Troublesome Creek, Kentucky, are a group of people living in a small, relatively isolated area who all have varying shades of blueness to their skin. Dr. Madison Cawein researched the anomaly and isolated it to a recessive gene that caused the an absence of the enzyme diaphorase. Diaphorase converts converts methemoglobin, the blue, oxygen-depleted form of hemoglobin, back to the hemoglobin that gives oxygenated blood a red color.