The Fugates were a family that lives in Kentucky that had a rare condition known as Methemoglobinemia. This hereditary genetic disorder results in the person's skin a very dark shade of blue.
The first Fugate in the United States was a French orphan named Martin Fugate, who settled in Troublesome Creek in the hills of eastern Kentucky in 1820. He married a woman named Elizabeth Smith, who was said to be as pale and white as the mountain laurel that blooms every spring around the creek hollows.
Unbeknownst to either of them, by some incalculable odds, both possessed a recessive gene that led to four of the seven children of this union being born with blue skin. In those days in rural eastern Kentucky, there were no roads, and a railroad wouldn't even reach that part of the state until the early 1910s.This kind of genetic isolation allowed for the continued reproduction and expression of the Fugate family's “blue skin” gene. As a result, many of the Fugates began to marry and have children within their bloodline.
Using research collected from studies of isolated Alaskan Eskimo populations, Cawein was able to conclude that the Fugates carried a rare hereditary blood disorder that causes excessive levels of methemoglobin in their blood. Methemoglobin is a nonfunctional blue version of the healthy red hemoglobin protein that carries oxygen. In most Caucasians, the red hemoglobin of the blood in their bodies shows through their skin giving it a pink tint.
For the Fugate family, the excessive amount of blue methemoglobin in their blood turned their skin color blue. This blood disorder is the result of a recessive gene, and so requires that both parents of a child have the recessive gene for the disorder to appear in their offspring. Without the Fugate's intense isolation and inbreeding, this disorder would be incredibly rare in their bloodline.