Creutzfeldt-Jakob disease (CJD) is a devastating, fatal illness that affects the brain. Fortunately, it is rare and only strikes one in a million people.

The mad cow disease outbreak in the United Kingdom in the 1980s has caused about 150 cases of CJD so far. However, no cases of CJD have been connected with beef consumption in the United States.

Scientists now believe CJD is caused by a type of protein called a prion (pronounced “pre-on”). These proteins naturally exist in the bodies of humans and other mammals and usually cause no harm, but if they take on a slightly different folded shape, they can cause disease. Scrapie (a disease of sheep and goats) and bovine spongiform encephalopathy (BSE, or “mad cow disease”) are also prion diseases. Other animals such as cats, monkeys, mink, deer and elk can be affected by prion diseases.

The general term for all these diseases is “transmissible spongiform encephalopathies.” “Spongiform” means filled with holes, like a sponge. “Encephalopathy” means a disease of the brain. Thus, Creutzfeldt-Jakob disease and the other transmissible spongiform encephalopathies destroy brain tissue and cause a sponge-like appearance of the brain.

About 300 new cases of CJD occur in the United States each year. About 90 percent of these cases are diagnosed as “sporadic” or “classical” CJD. This type occurs for no known reason. The leading theory is that normal prions spontaneously change into the infectious form. The average age at diagnosis of sporadic CJD is 60 years, and patients usually die within a few months.

Hereditary CJD accounts for 5 to 10 percent of cases each year. In this type, which runs in families, patients inherit a gene that mutates normal prions into disease-causing prions. Less than 5 percent of CJD patients in the United States acquire the disease accidentally during medical procedures. CJD can be transmitted by infected surgical equipment during brain surgery, by an infected cornea during a transplant operation or by the injection of infected human pituitary growth hormone (since 1985, all growth hormone used in the United States is synthetic, with no risk of CJD).

Since 1996 through late 2004, 158 people worldwide have been diagnosed with “variant” CJD, caused by eating beef infected with bovine spongiform encephalopathy. All but a few of these cases occurred in the United Kingdom, which had the highest rates of BSE in cattle. Variant CJD shows up in younger people; the average age at diagnosis is 29 years. The incubation period (time from eating infected beef until becoming ill) is thought to be about 12 years.

The illness may last more than a year before causing death.

Variant CJD might be transmitted via blood transfusions, so the Red Cross does not accept blood from people who spent 6 months or more in Europe or 3 months or more in the United Kingdom between 1980 and the present. Since all types of CJD affect the brain, the symptoms include personality changes, depression, problems with thinking, memory and judgment, muscle spasms and weakness, balance problems, vision changes, hearing difficulties and an inability to speak. Some patients have a loss of facial expression. All patients have dementia, similar to Alzheimer’s disease, but with a much more rapid onset.

Creutzfeldt-Jakob disease may be mistakenly diagnosed as a psychiatric illness, Alzheimer’s disease or other rarer types of dementia, or other types of encephalitis. To definitively diagnose CJD, a brain biopsy or autopsy is needed. However, an electroencephalogram (EEG) can be done, which may show electrical changes in the brain that are characteristic of CJD. Other helpful tests include MRIs, CT scans and lumbar punctures. There are no blood tests for CJD.

Sadly, there is no treatment for CJD other than pain medication, if needed, and medicines to relieve muscle spasms.

Kathryn B. Brown is a family nurse practitioner with a master’s degree in nursing from OHSU. Is there a health topic you would like to read about? Send ideas to kbbrown@eastoregonian.com. You can find more local health news and information in the Health section at www.dailyastorian.info.