In an unusual story that involves both genetics and geography, an entire family from isolated Appalachia was tinged blue. Their ancestral line began six generations earlier with a French orphan, Martin Fugate, who settled in Eastern Kentucky.

The Fugates, a family that lived in the hills of Kentucky, commonly known as the "Blue Fugates" or the "Blue People of Kentucky", are notable for having been carriers of a genetic trait that led to the disease methemoglobinemia, which gives sufferers blue-tinged skin.

Martin Fugate and Elizabeth Smith, who had married and settled near Hazard, Kentucky, around 1800, were both carriers of the recessive methemoglobinemia (met-H) gene, as was a nearby clan with whom the Fugates descendants intermarried. As a result, many descendants of the Fugates were born with met-H.

Descendants with the disease gene continued to live in the areas around Troublesome Creek and Ball Creek into the 20th century, eventually coming to the attention of the nurse Ruth Pendergrass and the hematologist Madison Cawein III, who made a detailed study of their condition and ancestry.

Cawein treated the family with methylene blue, which eased their symptoms and reduced the blue coloring of their skin. He eventually published his research in the Archives of Internal Medicine in 1964.

Benjamin Stacy, born in 1975, is the last known descendant of the Fugates to have been born exhibiting the characteristic blue color of the disease and lost his blue skin tone as he grew older.

It has been speculated that some other American sufferers of inherited methemoglobinemia may also have had Fugate ancestors, but searches for direct links have so far proved inconclusive.