Creutzfeldt-Jakob Disease (CJD) is an infectious disease that causes the brain to degenerate. The hallmark of this disease is mental deterioration and involuntary muscle spasms. Over time, the disease causes growing problems along with memory, personality changes, and dementia.

It is a type of transmissible spongiform encephalopathies (TSEs) or prion disease. These types of diseases can spread between human and animals.

Spongiform refers to the way the brain will start to develop holes in it. The holes give the brain a similar appearance to a sponge. Prion refers to a mutated protein that you may spontaneously develop, come in contact with, or inherit.

CJD is a rare and often fatal disease with about 350 new cases diagnosed in the United States each year.

There are three types of CJD including:

  • sporadic CJD: accounts for about 85 percent of new cases with the person having no known risk factors
  • hereditary CJD: accounts for about 10 to 15 percent of new cases and develops due to an inherited genetic defect
  • acquired CJD: accounts for remaining cases of CJD and occurs from exposure to infected nervous system tissue and infected meat

CJD progresses rapidly. About 70 percent of people diagnosed die within 1 year. The Centers for Disease Control and Prevention (CDC) noted that in 2020 about 538 people died from the disease.

CJD often starts with a sudden onset of cognitive impairment and issues with movement. For sporadic and hereditary CJD, the average age of onset is between 40 and 60, while acquired forms have an average age of onset of 28 and typically affect younger adults.

Symptoms of CJD often start as barely noticeable and then rapidly progress. These typically include:

  • dementia
  • loss of balance or coordination
  • changes in personality and behavior
  • confusion or disorientation
  • convulsions/seizures
  • muscle changes including loss of mass, weakness, and tremors
  • insomnia
  • difficulty talking
  • blindness or vision impairment
  • depression
  • coma
  • increased risk of infections

Though these symptoms typically describe all three types of CJD, acquired CJD has three notable differences. They include:

  • age of onset typically occurs in teens and 20s
  • the progression of the disease takes a longer time
  • the psychiatric symptoms tend to be worse

General scientific consensus states that CJD occurs due to abnormal changes to cellular proteins called prions.

In brief, prions perform a specific function within cells and is most abundant in the central nervous system. When you develop sporadic or inherited CJD, one of the proteins responsible for creating prions becomes abnormal and produces an infected prion.

The infected prion then spread through the central nervous system in a chain reaction or like dominoes getting knocked over until it eventually reaches the brain and causes the development of lesions or holes.

The chain reaction is similar in all three types of CJD. But they do differ in how the infected prion gets started. Here’s how they break down:

  • sporadic CJD: An error within your cells creates the infected prion. This is more common in advanced age.
  • hereditary CJD: A change in your genetic code creates an infected prion, which you can then pass on to your children through sperm or egg cells.
  • acquired CJD: In acquired forms, including variant CJD, the prion comes from outside of the body, often in the form of eating infected meat.

CJD and mad cow disease

There’s strong evidence that the agent responsible for bovine spongiform encephalopathy (BSE) in cows, commonly called “mad cow disease,” is also responsible for one form of acquired CJD in humans, called “variant CJD.”

BSE affected cattle in the United Kingdom, primarily in the 1990s and early 2000s. Variant CJD (vCJD) first appeared in humans in 1994–1996, about a decade after people first had extended exposure to potentially BSE-contaminated beef.

According to the CDC, this fits the known incubation periods for CJD. The CDC also notes that experimental studies on mice have also provided evidence supporting the link between BSE and vCJD.

Three types of CJD can occur, including sporadic, hereditary, and acquired. Though they are all rare, sporadic is the most common, followed by hereditary, and finally acquired.

Sporadic CJD

Sporadic CJD can develop anytime between the ages of 20 and 70. However, it most commonly affects people in their 60s. Sporadic CJD does not occur due to contact with infected meats, such as with mad cow disease.

Sporadic CJD occurs when normal proteins spontaneously mutate to the abnormal prion type. According to NINDS, around 85 percent of CJD cases are the sporadic type.

Hereditary CJD

Hereditary CJD accounts for 5-15 percent of CJD. It occurs when you inherit a mutated gene associated with prion disease from a parent. People with inherited CJD often have family members with the disease. The extent of how CJD manifests in separate family members can vary widely and is known as variable expressivity.

Acquired CJD

Acquired CJD, which vCJD (mad cow disease) is a part of, occurs in both animals and humans. It typically affects people in their teens and 20s.

You can become infected with acquired CJD by eating meat that’s contaminated with infectious prions. However, your risk of eating infected meat is very low.

You can also become infected after receiving blood or transplanted tissues, such as a cornea, from an infected donor.

The disease can also be transmitted by surgical instruments that haven’t been properly sterilized. Risk of this is low, though. That’s because there are rigorous sterilization protocols for instruments that have been in contact with tissue at risk for prion exposure, such as brain or eye tissue.

Despite media attention on mad cow disease, vCJD is very rare. According to the CDC, only four people from the United States have ever become infected with vCJD.

The risk of acquired CJD increases with age. You can’t get CJD from casual exposure to people who are infected. Instead, you need to be exposed to infected bodily fluids or tissue.

If you have a family member who developed hereditary CJD, you have a higher risk of developing CJD.

Acquired CJD is not always easy to diagnose. In fact, since 2018, the CDC has changed their diagnostic criteria to state that the only way to confirm diagnosis of CJD is through testing brain tissue, which is done at the time of autopsy.

Still, a doctor can test for and determine a probable diagnosis of CJD in living people. Two tests doctors use — together with clinical symptoms — to make a probable diagnosis include:

  • real-time quaking-induced conversion (RT-QuIC): looks for abnormal prions in spinal fluid
  • magnetic resonance imaging (MRI): to look for degeneration within the brain

Often, these tests along with clinical symptoms is enough for a probable diagnosis, but a doctor may order an electroencephalogram (EEG) for an additional scan of the brain.

A doctor can, however, diagnose hereditary forms of CJD based on:

  • review of family medical history
  • appearance of clinical symptoms
  • genetic testing to find variants in the PRNP gene

If you have a family member who developed hereditary CJD, you should consider genetic counseling.

No known cure or effective treatment for CJD exists.

However, doctors may prescribe medications to help ease symptoms. Some possible medications include:

  • opiate drugs for pain relief
  • clonazepam and sodium valproate for muscle spasms
  • intravenous fluids
  • feeding tubes

Researchers have tried several different treatment approaches, including:

  • antiviral agents
  • amantadine
  • antibiotics
  • steroids
  • interferons
  • acyclovir

Unfortunately, none of the tested methods have shown consistent, positive results in humans.

CJD has a very high mortality rate with about 70 percent of people diagnosed passing away within a year.

Symptoms of CJD will typically get worse until you lapse into a coma or develop a secondary infection. The most frequent causes of death for people with CJD include:

  • pneumonia
  • other infections
  • heart failure