Sept. 25, 2013 -- The most famous "blue man" -- known as "Papa Smurf" -- has died.

Paul Karason was born a fair-skinned, freckled boy with reddish blond hair. But later, he developed skin with a bluish tinge against his shock of white hair, the result of a rare medical syndrome known as argyria or silver poisoning from dietary supplements.

Karason died at the age of 62 this week after being treated for pneumonia at a Washington hospital after having suffered a heart attack. He'd also previously had a severe stroke, his estranged wife Jo Anna Karason told NBC's Today.

ABCNews.com interviewed Karason in 2008. At the time he lived in Oregon. He said the blue tinge had started more than a decade before that when he saw an ad in a new-age magazine promising health and rejuvenation through colloidal silver. He drank about 10 ounces a day of the home-brew that he dissolved in water.

Paul Karason Hailed as a Medical Mystery

Karason said he hadn't even realized his skin had turned a shade of blue until an old friend came to visit.

"And he looks at me and he says, 'What have you got on your face?' 'I don't have anything on my face!'" Karason said. "He says, 'Well, it looks like you've got camouflage makeup on or something.' And by golly, he came in and he was very fair-skinned, as I used to be. And that's when it hit me."

In those first months, he didn't notice a change in his skin color. But there were changes in his health.

"The acid reflux problem I'd been having just went away completely," he said. "I had arthritis in my shoulders so bad I couldn't pull a T-shirt off. And the next thing I knew, it was just gone."

As for whether it was the colloidal silver that had cured him, Karason said, "there's not the slightest doubt in my mind." As recently as the 1950s, colloidal silver was a common remedy for colds and allergies.

Fugates of Kentucky Had Skin 'Bluer Than Lake Louise

Karason became an Internet sensation, as were many others who have blue-shaded skin. The most notorious -- the Blue Fugates of Kentucky -- lived in an isolated pocket of Appalachia, passing down a recessive gene that turned their skin blue. Doctors don't see much of the rare blood disorder today.

Their ancestral line began six generations earlier with a French orphan, Martin Fugate, who settled in Eastern Kentucky.

Then there was Kerry Green , a "blue baby" born in 1964 in Tulsa, Okla. His family was given little hope that he would live because of a malformed aorta. But by 3 years old and several heart surgeries later, Green was being described by doctors as a "miracle child," small for his age at 23 pounds, but a "real live wire."

What doctors didn't know then was that the boy had a more serious underlying condition, a rare blood condition called methemoglobinemia -- the same disorder that affected the Blue Fugates of Kentucky.

"I was picked on as a kid in elementary school because I am blue," said Green. "I look dead. My lips are purple and my fingernails and toes are dark."

At the time, Green lived in Seattle and was disabled, but he said he believed finding a genetic connection to the Fugates might help him learn more about the father he never knew.

"I am positive my father had the condition," said Green. "I did see one kind of blurry picture of him and you could almost see it. He's got the pale look I do."

Bob Green, who would be about 74, had been a long-haul truck driver with relatives who had migrated west from Tennessee.

A sister was put up for adoption and Green doesn't know the whereabouts of two brothers. His mother wandered in and out of his life and he was raised by his grandparents.

"I just want to know where I came from and to know that side of my family history," said Green. "It's hard to describe and it's kind of weird not knowing where the condition of mine came from. People have pointed out the Fugates to me before."

In the 1980s and 1990s, those mountain people dispersed, and the family gene pool became much more diverse. Other relatives, perhaps like Green's paternal relatives, scattered throughout Virginia and Arkansas.

Even today, "you almost never see a patient with it," said Dr. Ayalew Tefferi, a hematologist from Minnesota's Mayo Clinic. "It's a disease that one learns about in medical school and it's infrequent enough to be on every exam in hematology."

In the mildest form, methemoglobinemia causes no harm, and most of the Fugates lived well into their 80s. But in Green's case, his body is starved of oxygen and every organ is affected.

Methemoglobinemia is a blood disorder in which an abnormal amount of methemoglobin -- a form of hemoglobin -- is produced. Methemoglobin cannot effectively release oxygen.

Hemoglobin is responsible for distributing oxygen to the body and without oxygen, the heart, brain and muscles can die.

"I don't breathe very well," said Green. "The red blood cells don't give me enough oxygen."

Green's condition was such an anomaly that hematologists at the Dana Farber Cancer Institute in Boston paid for him to fly East several years ago just to study him.

Most of what is known about methemoglobinemia comes from one doctor's study of the Fugate ancestry in the early 1960s. Dr. Madison Cawein III, a hematologist at the University of Kentucky's Lexington Medical Clinic, drew family charts and blood samples to better understand the genetic disorder.

The most detailed account, "Blue People of Troublesome Creek," was published in 1982 by the University of Indiana's Cathy Trost.

The last in the direct line of Fugates to inherit the gene was Benjamin "Benjy" Stacy, whose skin at birth was "as Blue as Lake Louise," according to doctors at the time. He now lives in Alaska, according to Facebook.

Green is not the only person to wonder if there is a genetic connection to the Blue Fugates.

Jennifer L. Adams Horsley of Hartford, Ind., told ABCNews.com in 2012 that she is certain that her mother-in-law, Amanda Susan Parker Horsley, was descended from the family.

"She was from the upper regions of Kentucky," she said. "Her lips and nail beds were perpetually blue."

"They were like that almost all the time," said Horsley, 62, a retired nurse. "The color depended on when she got upset or was cold. It was so pronounced that everybody thought she was sick."

Parker died at 73 of liver cancer nine years ago, "So we may never know," said her daughter-in-law.

The family presumes that Parker's mother, Mary McCleese Parker, also had the condition. "My grandmother was blue," said Horsley's husband John H. Horsley. "Everyone thought it was real odd."

He grew up in Ohio, but his parents had met in Carter County, Kentucky. The Horsleys said they know of no other children or grandchildren who inherited the gene for methemoglobinemia.

"It was never diagnosed and doctors were baffled," said Jennifer Horsley. "I don't think they had even heard the name."

Methemoglobinemia may be passed down through families or can be caused by exposure to certain drugs, chemicals or foods.

In Green's case, the disorder was genetic and occurs when there is a problem with the enzyme called cytochrome b5 reductase.

In type one, the red blood cells lack the enzyme. In type 2 -- also called hemoglobin M disease -- the enzyme doesn't work anywhere in the body.

Green has M disease, which is caused by defects in the hemoglobin molecule itself and can be passed down from only one parent.

The disorder once saved his father's life, according to a story told by Green's mother. "A woman shot him five times and he didn't bleed out because his blood was so thick."

For that very reason, Green takes three different blood-thinning drugs to prevent blood clots and morphine for the pain.

"I have found a way to live around it the best I can," he said. "It's caused me a lot of emotional problems.

As for finding his father, "I would really like to know more about how he grew up with it and how he dealt with it. My father and I never met, but come to find out, we are a lot alike."