Skip to content
Help Lito

Understanding CJD

Creutzfeldt-Jakob Disease, explained carefully.

This page explains what CJD is, why it is so hard, and why time matters. It is written for families, journalists and curious visitors first, with deeper detail available for professionals. It is not medical advice.

  1. 01

    A normal protein

    Every person makes prion protein (PrP). In its normal shape it is harmless.

  2. 02

    Misfolding

    In CJD, some PrP takes on an abnormal shape that the body cannot easily clear.

  3. 03

    A chain reaction

    Abnormal PrP induces normal PrP to misfold too. The process spreads through brain tissue.

  4. 04

    Neurological damage

    Nerve cells are lost. Coordination, vision, memory, speech and movement decline, often within months.

01

What is CJD?

Creutzfeldt-Jakob Disease (in Portuguese, Doença de Creutzfeldt-Jakob, DCJ) is a rare, rapidly progressive, neurodegenerative disease. It belongs to a family called prion diseases. The disease involves the prion protein, which every person makes, adopting an abnormal shape that spreads through the brain and damages nerve cells. Most cases are sporadic, meaning they occur without a known cause. Smaller proportions are genetic or acquired.

For professionals

CJD is a transmissible spongiform encephalopathy caused by the conformational conversion of cellular prion protein (PrP^C) into a misfolded, aggregation-prone isoform (PrP^Sc). Sporadic CJD accounts for roughly 85% of cases, genetic forms for 10 to 15%, and acquired forms (iatrogenic, variant) for a small minority. Subtypes are classified by PRNP codon 129 genotype and PrP^Sc glycotype.

02

What does "prion disease" mean?

A prion is a protein that has misfolded in a way that causes other copies of the same protein to misfold too. The word comes from "proteinaceous infectious particle". Unlike bacteria or viruses, there is no genetic material involved in the spread of the abnormal shape inside the brain. That is part of why prion diseases are so difficult: the thing causing damage is a version of something the body normally makes.

03

Why is it difficult?

CJD is rare, so most physicians see very few cases. Its early symptoms overlap with many other conditions, including encephalitis, autoimmune disorders, strokes and other dementias. Diagnosis usually requires a combination of clinical assessment, MRI, EEG, and tests on cerebrospinal fluid. Because the disease moves quickly, the window in which a diagnosis can be confirmed and options evaluated is short.

For professionals

Supportive tests include DWI/FLAIR MRI showing cortical ribboning or basal ganglia signal, periodic sharp wave complexes on EEG, and CSF markers such as 14-3-3, total tau and, with high specificity, RT-QuIC. Definitive diagnosis is neuropathological.

04

Why does time matter?

CJD typically progresses over months. Patients lose coordination, vision, memory, speech and movement. Public health authorities state that there is currently no proven treatment capable of stopping or reversing the disease. Every week matters for care decisions, for understanding the available research, and for any conversation with a specialized team.

05

Can you catch it from someone?

No. Sporadic CJD is not spread by ordinary social contact. Family members, caregivers and people interacting normally with a patient are not at increased risk because of everyday contact. Standard precautions are used in specific medical settings, such as neurosurgery, but this has nothing to do with being near a person.

06

What research is happening?

A small, specialized research community has spent years on prion disease. Work includes reducing the amount of normal prion protein in the brain with RNA-targeting therapies, better biomarkers for earlier diagnosis, and methods to track how the disease progresses. One PrP-targeting siRNA is now in a first-in-human safety study. This is early-stage research, not an available treatment.

07

Symptoms

Symptoms vary between people and change over time. They may include:

  • Loss of coordination
  • Motor impairment
  • Visual disturbances
  • Cognitive changes and memory problems
  • Myoclonus (sudden muscle jerks)
  • Behavioral changes
  • Speech impairment
  • Rapid neurological decline

Medical information on this page is drawn from the US CDC and NINDS, and from the peer-reviewed literature summarized on our Sources page. Sources

Go to the research section