ABCNews.com was unable to determine if Benjamin Stacy is still alive -- he would be 37 today. Trost writes that he eventually lost the blue tint to his skin, but as a child his lips and fingernails still got blue when he was angry or cold.
His mother Hilda Stacy, who is 56, appears to still live in Hazard, Ky., but did not answer calls to her home. Other relatives are scattered throughout Virginia and Arkansas.
Most of what scientists know about the family was discovered by Cawein, the grandson of Kentucky's poet laureate, who had done pioneering research on L-dopa as a treatment for Parkinson's disease.
Later in 1965 he was famous for another reason. His wife was murdered by chemical poisoning, but no one was ever indicted.
Cawein heard rumors about the Fugates while working at his Lexington clinic and set off "tromping around the hills looking for blue people," according to Trost's account.
At an American Heart Association clinic in the town of Hazard, Cawein found a nurse, Ruth Pendergrass, and she was willing to assist. She remembered a dark blue woman who had come to the county health department on a frigid afternoon seeking a blood test.
"Her face and her fingernails were almost indigo blue," she told Trost. "It like scared me to death. She looked like she was having a heart attack. I just knew that patient was going to die right there in the health department, but she wasn't a'tall alarmed. She told me that her family was the blue Combses who lived up on Ball Creek. She was a sister to one of the Fugate women."
More families were found -- Luke Combs, and Patrick and Rachel Ritchie, who were "bluer'n hell" and embarrassed by their skin color.
Cawein and Pendergrass began to ask questions -- "Do you have any relatives who are blue?" -- and mapped a family tree and took blood samples.
The doctor suspected methemoglobinemia and uncovered a 1960 report in the Journal of Clinical Investigation. Dr. E. M. Scott, who worked in public health at the Arctic Research Center in Anchorage, had seen a recessive genetic trait among Alaskans that turned their skin blue.
That suggested an inbred line that had been passed from generation to generation. To get the disorder, a person would have to inherit two genes -- one from each parent. When both parents have the trait, their children have a 25 percent chance of getting the disorder.
Scott speculated these people lacked the enzyme diaphorase in their red blood cells. Normally diaphorase converts methemoglobin back to hemoglobin.
All of the blue Fugates he tested had the enzyme deficiency, just like the Alaskans Scott had observed.
Their blood had accumulated so much of the blue molecule that it over-powered the red hemoglobin that normally turns skin pink in most Caucasians.
The bluest of the bunch was Luna, and she lived a healthy life, bearing 13 children before she died at the age of 84.
As coal mining arrived in Kentucky in 1912 and the Fugates moved outside of Troublesome Creek, the blue people began to disappear.
Doctors say Benjy likely carried only one gene for methemoglobinemia, because he eventually had normal skin tones, and the likelihood of him marrying a woman with the same recessive gene would have been small.
By the time reports appeared in the media on the disorder, the Stacy family was upset with insinuations about in-breeding that fed into stereotypes of backwoods Appalachia.
"There was a pain not seen in lab tests," wrote Trost. "That was the pain of being blue in a world that is mostly shades of white to black."