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DEAR DR. ROACH: Have you ever discussed prion disease in your column? It afflicts one in 1 million people, swiftly kills its victims in a matter of days, and is incurable. People commonly know it as "mad cow disease." I recently lost a great friend to a prion disease, and she truly was one in a million. It's a nightmare to endure. — R.
ANSWER: There are three different prions that affect humans, with various ways in which a person can acquire the disease. Of these, the most common is Creutzfeldt-Jakob disease (CJD), which I assume is what you're talking about.
The most common form is called sporadic CJD (sCJD), which is thought to be caused by a person getting a mutation in the PRNP gene. This causes a protein (a prion protein) to be misfolded, which, in turn, causes normal prion proteins to be misfolded. These abnormal proteins are deposited in the brain and interfere with normal brain activity, causing many different symptoms (especially dementia but movement disorders as well).
sCJD affects approximately one per 1 million people. Rather than days, death usually occurs in a span of about six months — but not commonly longer than a year. You're correct that there isn't a cure.
"Mad cow disease" is called variant CJD (vCJD). There have been just over 200 cases that were ever reported in the world's literature, mostly from the United Kingdom. It's caused by eating meat from a cow with a very similar disease — bovine spongiform encephalopathy. vCJD is similar to sCJD clinically. The most recent reported case was from a lab worker in 2021, and there haven't been any cases that were reported from animal exposure since 2014. There's also a rare familial form of CJD, called fCJD.
CJD can also be spread through medical procedures. Decades ago, hormones were acquired from the pituitary glands of cadavers, and the lining of the brain from the cadavers was used in surgery to repair damage to a person's meninges (called a dural graft). It doesn't appear that any cases have been transmitted this way since 1985.
I'm very sorry about your friend. Degenerative neurological diseases, of which there are many (but most are fortunately rare), are horrible for patients and their loved ones to endure.
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Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to ToYourGoodHealth@med.cornell.edu.
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