What is CJD?

Creutzfeldt-Jakob Disease is one of a group of rare brain disorders known as prion diseases that occur both in humans and certain animals.

In these diseases, brain cells undergo degeneration and eventually die leaving microscopic holes in the brain tissue (described as ‘spongiform’ change).

The precise disease mechanism responsible for the degeneration of the brain cells is uncertain. However, there is an associated deposition of a protein (called PrPSc ) which is an abnormally folded form of a normal body protein (called PrPC).

The cause of this disease process varies with disease type:

  • In sporadic CJD, there is no known cause and it appears to be a spontaneous process, perhaps resulting from a random error in protein processing.
  • In acquired forms of CJD (iatrogenic or variant), an infectious agent (named the ‘prion’) causes the disease process. The precise nature of the prion is uncertain but it is widely believed to consist at least mainly of PrPSc and it is known that PrPSc can interact with the normal PrPC and convert it to create more PrPSc. Following infection, there may be a delay of several to many years before disease becomes evident. In variant CJD, the prion originated from BSE-infected cattle; in iatrogenic CJD, the prion originates from disease-affected humans.
  • In genetic CJD, a mutation abnormality in a gene, the one responsible for prion protein production, (called PRNP) is the fundamental cause. The gene abnormality leads to abnormal protein production that then leads on to PrPSc in the brain. The inheritance of these mutations is ‘autosomal dominant’ which means that an affected parent has a 50:50 chance of passing it on to any offspring. Despite the gene mutation being present from the point of conception, disease may not arise until later in life.

Types of CJD

There are four types of CJD: Factsheets on each type can be downloaded from the links below

Sporadic CJD (or classical CJD) is the most common form, accounting for around 85 per cent of cases. The cause is unknown. It mainly affects the over 50s and has a rapid onset. The course of the disease is usually measured in months.

Genetic CJD (sometimes known as famillal CJD) is an inherited form of the disease, with younger onset and a longer time course than sporadic CJD.

Iatrogenic CJD occurs through contamination with infected tissue via medicalprocedures, for example, the use of human growth hormone, blood transfusionor surgical instruments.

Variant CJD is caused by exposure to bovine spongiform encephalopathy, or BSE , and typically affects younger people. It has a relatively longer time course - an average 14 months from onset of symptoms to death. There is a combination of psychiatric, neurological and physical symptoms.

Symptoms of CJD

  • The precise symptoms and clinical time course of CJD vary according to the type of disease.
  • Details for the particular types can be found in our separate Fact Sheets.
  • However, in all types, the symptoms reflect brain dysfunction and certain features are common in all types: memory problems, confusion, clumsiness, unsteadiness and jerky movements with progressive disability leading to loss of awareness, loss mobility, loss of speech, incontinence and the need for full nursing care.
  • In sporadic CJD, the progression is typically very rapid with death occurring after a few weeks to months although it can be slower in a small number of cases.
  • In variant CJD, early symptoms are often more psychiatric in nature (such as anxiety or depression) with behavioural changes (such as agitation or social withdrawal). Progression is usually slower than that in sporadic CJD, with the later appearance of unsteadiness, incoordination and other clearly neurological problems, resulting in death generally after 1-2 years.