퇴행성 뇌질환 - 2. CJD(Creutzfeldt-Jakob Disease)’s Overview

▣ CJD(Creutzfeldt-Jakob Disease)’s Overview

The disease was first described by German neurologist Hans Gerhard Creutzfelt in 1920 and shortly afterwards by Alfons Maria Jakob, giving it the name Creutzfeldt-Jakob. Some of the clinical findings described in their first papers do not match current criteria for Creutzfelt-Jakob disease, and it is considered highly likely that at least two of the patients in initial studies were suffering from a different ailment.

Creutzfeldt-Jakob disease (CJD) is a rare, fatal brain disorder associated with a misshapen protein in the brain, known as a prion. Although prion-associated diseases are not well understood, scientists theorize that prions cause damage by causing healthy proteins in the brain to take the prion shape, so these too become damaging particles. This slow chain reaction of damaged proteins occurs over many years and results in brain damage.

When symptoms eventually appear, CJD causes rapidly progressive dementia (mental decline) and involuntary jerking muscle movements called myoclonus. About 90% of people with CJD die within 1 year of diagnosis.

CJD is considered an infectious illness. However, prions do not move easily from one person to another. Most cases of CJD are not caused by exposure to another person with the disease but by an accidental mutation in brain cell DNA that allows a prion particle to be formed. This mutation can be sporadic (occurring for the first time in a family, without a family history of the same gene mutation and disease) or hereditary (passed down from parent to child). Most cases of CJD are sporadic. Between 5% and 15% are caused by inheritance of the gene mutation that encodes the prion protein. Jewish people born in Czechoslovakia, Chile and Libya have a higher-than-average number of inherited cases of CJD. Because the effects occur very slowly, inherited CJD does not cause symptoms until adulthood.

A type of CJD called 'variant CJD' shows somewhat slower progression of brain injury and more psychiatric symptoms, and it tends to affect younger people. This type of CJD has been linked to eating beef from cattle infected with bovine spongiform encephalopathy (BSE), also called '‘mad cow disease'. Beef products from infected cows can contain prion particles, which is why they can pass infection to people. This small outbreak of variant CJD was described in the United Kingdom and peaked in 1999. Since then, changes in beef farming and processing practices have helped to limit the number of new cases. All but 11 cases of variant CJD occurred in the United Kingdom. Seven cases have been diagnosed in France, and one case has been diagnosed in Italy. Three other countries (Canada, Ireland and the United States) have each had one case, all in travelers who had been in the United Kingdom and had eaten beef there during the outbreak years.

It is extremely uncommon for this disease to spread from one person to another, but in recent years, three people have acquired variant CJD after receiving blood transfusions. These cases prompted blood banks to start using extra precautions, such as preventing people in the United States from donating blood if they lived in a country where BSE is common for more than 3 months. It is possible to spread CJD (and presumably variant CJD) during medical procedures because it can spread on contaminated equipment such as surgical instruments and brain electrodes. Also, the illness can be spread by contaminated tissue, such as corneas that are used for transplant, and injections of pituitary gland extracts containing human growth hormone or injections of human gonadotropin hormones, which have been used to treat infertility. Synthetic hormones do not pose any risk of CJD.