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Scientists are digging into the past in search of genetic insight into modern skin diseases. Here are some of the hottest topics in the study of human history and skin disease.
The ancient Greeks and Romans had an itch. Plenty of them, in fact, since psoriasis was a major nuisance in their time.
So, it turns out, were plenty of other skin diseases. Historical records and examinations of mummies are turning up familiar conditions in ancient and prehistoric people like dandruff, lice, eczema and skin cancer. Even tattoos, dyed hair and signs of skin bleaching are appearing in the preserved bodies of humans who lived thousands of years ago.
“Everything I saw in mummies, I can see in live, modern-day humans,” says dermatologist Kieron Leslie, M.D., an associate professor at the University of California at San Francisco who has studied skin disease in the past.
There’s plenty more to learn than details about the rashes, lesions and pustules that bedeviled our ancestors. Scientists are digging into the past in search of genetic insight into modern skin diseases. And historians seek signs of how these illnesses were treated - for better and for worse.
Here’s a look at some of the hottest topics in the study of human history and skin disease.
Ötzi the Iceman, who lived about 5,000 years ago in the Alps, is perhaps best known as the possible victim of homicide. But the mummified man was also a standout when it comes to remarkably revealing skin.
In addition to 61 charcoal tattoos of black lines and crosses, an examination revealed that had three Beau’s lines on his remaining fingernail - potentially a sign of infection or injury. He also has a cut on his right hand, possibly from a wound related to his killing.
In a 2006 report [Int J Dermatol. 2006 Feb;45(2):161-3.], Dr. Leslie and a colleague note this and other signs of ancient skin disease in mummies. The preserved head of Egypt’s King Ramses V (circa 1150 B.C.), for example, shows signs of smallpox. Other Egyptian mummies reveal benign and malignant tumors, including a possible histiocytoma and a lipoma.
Mummies from the last thousand years provide even more glimpses into skin disease of the past. Researchers found an ulcer linked to tertiary syphilis and a tumor linked to HPV type18 in a Renaissance Italy beauty named Maria of Aragon. And they uncovered leishmaniasis and head lice in an Andes mummy from around the year 1100.
Just this year, Greek researchers reportedly found possible signs of exogenous ochronosis, a response to bleaching chemicals, in the skin of a 3,500-year-old female mummy head from Egypt.
These kinds of findings are “a testament to the remarkable preservation of skin tissue,” Dr. Leslie says. “If you rehydrate the tissue, you can still see the structures like hairs.”
Dr. Leslie’s own research at the British Museum turned up dandruff, eczema, head lice and a possible case of pubic lice. “These diseases have obviously been with us for many thousands of years,” he says.
Historical records add a missing piece to the puzzle of Egyptian skin disease in particular. We know, for example, that Egyptians used tar to treat rashes and, presumably, eczema and psoriasis, Dr. Leslie says. Today, tar is a component of some shampoos that treat dandruff, and it’s mixed with a topical steroid to treat psoriasis, he says.
What’s next? Dr. Leslie says further research into preserved bodies from the past could offer insight into the evolution of skin disease. “They could give us a lot of clues about how diseases change over time,” he says, just like history tells us that syphilis acted differently hundreds of years ago.
Could leprosy be the oldest infection specific to humans? Xiang-Yang Han, M.D., Ph.D., thinks it is. He is a pathologist and professor at the University of Texas M.D. Anderson Cancer Center.
In a 2014 study, Dr. Han and a colleague report evidence that leprosy germs that began to evolve millions of years ago, possibly as long as 20 million years, and made their way into hominids.
The current species of leprosy bacteria “have adapted to live in human flesh that are normally sterile and guarded by our defenses, such as white blood cells,” Dr. Han says. That’s unlike many other bacteria, viruses and worms, he says, that live in non-sterile sites like the skin surface, the oral cavity and the lower gut.
History has more new things to tell us about leprosy.
Almost by definition, lepers are supposed to be isolated from society, perhaps quarantined on an island somewhere, to prevent the spread of the illness. “This practice caused a lot of miseries, horror, and stigma to the patients. But there were no better ways to control the disease then,” Dr. Han says. “It was a sacrifice of the small to the benefit of the large of a society.”
But historians are learning that isolation wasn’t always mandatory, especially in medieval times. “People were not necessarily segregated into leprosy hospitals or stigmatized in death, as we used to think. They were buried with the rest of their communities. I think people were more accepting,” says Charlotte Roberts, Ph.D., an associate professor with Durham University in the U.K. and president of the British Association of Biological Anthropology & Osteoarchaeology.
Monica Green, Ph.D., a professor who studies the history of medicine at Arizona State University, agrees. “We find a range of charitable and human treatment in the historical records,” she says. “To my mind, the worst periods for the segregation of persons suffering from leprosy were the isolation communities set up in the 19th and 20th centuries, mostly on islands.”
Even today, she says, leprosy sufferers can still worry about coming forward because of lingering stigma. (The disease is far from eradicated. According to the World Health Organization, 214,000 new cases were reported in 2014.)
“We have not yet figured out how to fully confront stigma in infectious diseases,” she says. “Education and human generosity are as important as scientific advances.”
There’s good news. Now, Dr. Han says, isolation isn’t needed because antimicrobial treatments stop the infectivity of leprosy in days.
In the bigger picture, he says, “we humans know how to eradicate leprosy. But, to achieve this, it is easier said than done. It will be a long way. There are still lots of hurdles ahead. Active participation of governments and societies, more health resources in terms of manpower, infrastructures, and education, and the attitude and knowledge of the patients and caregivers are all important aspects.”
Written records show that psoriasis affected ancient Greeks and Romans, but genetic research suggests that its roots go back further than that. Much, much further, says Omer Gokcumen, Ph.D., an assistant professor of biological sciences at the University of Buffalo.
“Our recent work has shown that the genetic variants that predisposes the skin to become psoriatic have been around for hundreds of thousands of years,” he says. “Whether they actually caused disease in ancestors of modern humans or a combination of these susceptibility variants with the environmental factors lead to the disease remains unknown.”
Professor Gokcumen and colleagues reported their findings about the genetics of psoriasis in 2015. [Mol Biol Evol, doi:10.1093/molbev/msu405]. They found evidence of ancient genetic links to not only psoriasis but also Crohn’s disease.
There’s a mystery lurking in all this. Why would natural selection preserve genetic traits linked to psoriasis? One possible answer: These traits could actually be good for us.
“It is plausible, based on our recent work and those of others, that traits that make the skin more ‘penetrant’ may expose the immune system to more allergens, pathogens, etc.,” he says. “The result is an active immune system with potential to develop immunity to diverse set of pathogens.”
In other words, he said, the genetic traits could produce a “natural vaccination.” However, “the downside of this overactivity may be autoimmunity.”
What does this all mean for medicine now and in the future? “What’s becoming clear is that psoriasis is a very complex disease and may be a combination of multiple genetic variants involved in immunity and skin development, as well as environmental conditions and interactions with the good and bad microbes,” Professor Gokcumen says. “Evolutionary genetics give us a framework to understand how these different factors can collectively act together. We are at the edge of major breakthroughs in general where the genomic and other technologies will finally give us insights into how we diagnose and treat psoriasis and other similarly complex diseases.”
So is it time to get excited? Well, he says, “we are not there just yet.”