The brain disease that killed Carol Baker, the subject of an emotionally wrenching obituary in our pages this week, is as bizarre as it is rare.

It literally pokes holes in the brain by turning ordinary bits of protein into roving cell-destroyers.

Sporadic Creutzfeldt-Jakob Disease, as it’s known, is related to the better-known Mad Cow disease and other fatal disorders such as fatal familial insomnia, which kills people through exhaustion from lack of sleep, and kuru, which strikes members of a tribe in Papua New Guinea.

They all share one thing in common: those renegade proteins, known as prions (pronounced PREE-ons). They aren’t bacteria or viruses or fungi, the usual causes of illnesses that are infectious, like Mad Cow Disease. Instead, they’re something completely — and mysteriously — separate.

D.T. Max, a staff writer at The New Yorker, wrote about these diseases in a 2006 book titled “The Family That Couldn’t Sleep: A Medical Mystery.” I interviewed him a few years ago about his book and called him today to ask about what we know about these disorders, which are inevitably fatal. This is a condensed version of our conversation.

What is a prion?

Prions are proteins that you have in every cell, but no one quite knows what they do. When a healthy prion becomes misformed, it can become lethal and act like a virus.

The prions gunk up and kill a cell, but that doesn’t kill the prions. They begin a forward motion that in turn causes other prions they come in contact with to misshape.

It’s a little like dominoes that keep falling: you get a visible formation of dead cells called a plaque. It looks white and it’s hard, and the brain can’t withstand that kind of insult.

You can see it in a microscope: where there should be cells, there are holes. That’s not good for anybody.

A cow gets Mad Cow disease by eating food that includes the remains of other cows that are infected. How does that work?

It would have ingested contaminated prions from other cows. The prions would go into the stomach and then work their way into the brain to create the symptoms.

People, in turn, get bovine spongiform encephalopathy — Mad Cow Disease — from eating beef from cows that were sick. What about sporadic Creutzfeldt-Jakob Disease, which struck the subject of our story? It occurs randomly, right?

The theory is that as you get older and your body works less well, one of the things it gets bad at is making proteins. They may be slightly defective, and it’s possible that a defective protein will assume an infectious shape and come in contact with other proteins that are healthy and cause those to develop problems.

But there are a lot of sensible, well-connected people in the field who don’t believe sporadic CJD exists. They think it’s an infection whose cause has not been found. We wouldn’t know the epidemiology since it takes so long for a person to develop it.

You write about Papua New Guinea, where a related disease called kuru still afflicts old people who have eaten the remains of other humans, even though they haven’t done that for a long time.

Some people are still becoming sick from eating infected human flesh, but the last cannibalistic feasts were 50 years ago.

Your book focuses on familial fatal insomnia. What happens to people who develop this condition?

A person loses the ability to sleep as part of the degeneration of their brain. They die in part from brain degeneration and in part from exhaustion.

What makes this disease run in families?

Your genes are responsible for the blueprint of your proteins. So if your genes are defective, they give wrong instructions.

What are the prospects for treatment for these prion diseases?

In England, they’ve effectively ended the Mad Cow epidemic and did a pretty good job of it. But that resulted in a decrease in urgency to solve this scientific riddle and a decrease in funding. Young researchers interested in the subject may have decided to go elsewhere.

I don’t know if we’re going to have good answers for a long time.

A note: After talking to Max, I discovered that there’s a new development in the fight against prion-related diseases. Last month, a study in the New England Journal of Medicine reported that some people in Papua New Guinea, where the kuru disease is found, have developed genetic resistance to the illness.

“This is thought be perhaps the strongest example yet of recent natural selection in humans,” says a press release. In other words, the bodies of some people developed a way to resist the illness and passed it on to their offspring: it appears to be a Darwinian case of survival of the fittest.

The press release quotes a researcher as saying: “Kuru comes from the same disease family as CJD, so the discovery of this powerful resistance factor opens up new areas for research taking us closer to understanding, treating and hopefully preventing a range of prion diseases.”


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