Creutzfeldt-Jakob disease (CJD)

Creutzfeldt-Jakob disease (CJD) is a rapidly progressive illness. It is one of a group of rare diseases that affect both humans and animals, known as transmissible spongiform encephalopathies (TSEs) or prion diseases. CJD is marked by physical deterioration of the brain, which commonly causes dementia and difficulty walking.

Death can occur up to two years after the first symptoms, but most people die within about six months. There is no treatment or cure.

CJD and other prion diseases#

CJD is the human form of TSE, or prion disease. This group of diseases occurs in humans and in animals such as cattle, sheep, elk and deer. CJD was first recognized in humans in the 1920s. The human prion diseases include:

• sporadic CJD, which causes about 85 to 90 per cent of cases
• genetic (familial) CJD, which causes about 10 to 15 per cent of cases
• Kuru
• variant CJD
• medically acquired CJD

Sporadic CJD accounts for the greatest number of human deaths from this group of diseases. CJD affects roughly one person per million each year, so in a population of 10 million there are likely to be at least 10 cases in a year. It most often affects people between 50 and 70 years of age. The cause of sporadic CJD is unknown.

Genetic CJD#

Genetic prion disease is extremely rare and is most often recognized from a family history of the illness in brothers, sisters or parents. It is an inherited disease, passed from a parent to a child at conception. It is not always passed on; each child has a 50 per cent chance of inheriting the disease.

Kuru#

Kuru is a human prion disease found only in the central highlands of New Guinea. It was caused by the practice of ritualized cannibalism of deceased relatives. That practice has stopped, and the number of Kuru cases has declined over time. Kuru has never been found outside this region.

Variant CJD#

Variant CJD was first recognized in 1996 in the United Kingdom. It is linked to an epidemic of bovine spongiform encephalopathy (BSE), known in the media as “mad cow disease”. BSE is a prion disease of cattle. The spread of scrapie, a naturally occurring TSE in sheep, to cattle through the food chain is thought to have caused the BSE epidemic in the United Kingdom in the 1980s.

Variant CJD differs from the other human prion diseases in several ways. The illness can last longer (up to a year) than sporadic CJD, people tend to develop it at a younger age, and autopsies reveal distinct changes in the brain not seen in other human prion diseases.

Medically acquired CJD#

Medically acquired CJD has occurred worldwide as a result of a number of medical treatments. Treatments shown to have transmitted CJD include:

• exposure to contaminated neurosurgical equipment (five cases recorded worldwide)
• the use of human pituitary extract hormone, for example for infertility or short stature
• dura mater grafts used in brain surgery to repair the membrane covering the brain
• corneal grafts (three cases recorded worldwide)

Hormone and graft treatments once used tissue taken from human cadavers that may have been contaminated with CJD. Once CJD was identified as a hazard, the use of these products was discontinued and replaced with synthetic alternatives. Sterilizing procedures were strengthened, patients were screened for CJD risk before neurosurgery, and stricter guidelines were set for organ transplants. Medically acquired cases have become very rare since these measures were introduced.

Blood transfusion and blood donation#

The possibility of transmitting CJD through blood transfusion or blood products is sometimes raised. There is no evidence that blood products cause sporadic or medically acquired CJD.

Variant CJD, however, has been confirmed to be transmissible through blood transfusion, both in the laboratory and through experience in the United Kingdom. In response, blood-banking guidelines in many countries defer donors who may have some risk of CJD.

Before donating blood, screening is used to identify potential donors who may have CJD, who may have been exposed through medical treatment, or who are relatives in families where a CJD-related death has occurred. These people are routinely asked not to donate. They include:

• first-degree relatives of people who have died from sporadic CJD
• families with genetic CJD
• recipients of human pituitary hormone extract
• anyone who received neurosurgery on the head, neck or spinal cord during the period when dura grafts may have been used

As a precaution, many countries also defer people who lived in the United Kingdom for a significant period during the years of the BSE epidemic, or who received a blood transfusion there during that time.

Diagnosis#

CJD is difficult to diagnose. Early symptoms can be vague, and there are no tests that can confirm exposure or diagnose CJD until symptoms are well advanced. As the disease progresses, extensive investigations are needed to rule out other treatable conditions. A possible diagnosis is therefore only made as the illness develops, and examination of brain tissue after death is the only way to confirm it definitely.

Symptoms of CJD#

The symptoms of CJD are caused by changes in brain tissue. They may include:

• confusion or disorientation that rapidly progresses to dementia
• personality and behavioral changes
• weakness, loss of balance and loss of muscle control, causing difficulty walking
• muscle spasms
• visual symptoms such as double vision or blindness

What happens in the brain#

Normal prion protein is made in the healthy brain. Although its function is not fully understood, prion diseases are caused when this protein changes its physical structure or shape. The abnormal prion protein causes damage and cell death in the brain. Once present, it is thought to act as a template, converting other normal prion protein into the abnormal, disease-causing form.

It is not known what triggers the first change to the prion protein. Possible influences include:

• genetic factors that may make some people more likely to spontaneously produce the abnormal prion protein
• changes in the brain’s chemical environment
• exposure to abnormal prion protein, for example through the medical exposures described above

CJD is sometimes referred to as a “slow virus”, but the viral theory has never been confirmed.

Sterilization and everyday contact#

The abnormal prion protein that causes CJD is extremely tough. It remains active outside the body and survives the routine sterilization used for other disease-causing agents such as viruses and bacteria. The higher levels of sterilization recommended for CJD exceed normal standards and cannot be used routinely, because they significantly damage medical instruments and equipment.

CJD is not transmitted by casual contact such as drinking from the same cup, kissing or other close physical contact with a person who has the disease.

In many places CJD is a notifiable disease, meaning that any newly diagnosed case must be reported to health authorities by the treating doctor.

Key points#

• death can occur up to two years after the first symptoms, but most people die within about six months
• there is no treatment or cure
• the cause of sporadic CJD is unknown
• Kuru was caused by the past practice of ritualized cannibalism and is no longer spreading
• variant CJD is linked to BSE (“mad cow disease”) and can be transmitted through blood transfusion

Where to get help#