WEDNESDAY, Feb. 18, 2003 (HealthDayNews) -- For the first time, scientists have found the protein-like structures associated with Creutzfeldt-Jakob disease in the areas of the nose that process smell.
The finding has important implications for diagnosing the condition and it also raises questions about how the disease is transmitted.
Creutzfeldt-Jakob disease (CJD), thought of as the human equivalent of mad cow disease, is a degenerative brain disease that causes dementia and death, usually within one year of onset. As of now, there's no way to confirm that a person has CJD short of a brain biopsy, which can only be performed after the person dies.
"If this is correct and confirmed by others, it offers the possibility that one day we may be able to do some form of a nasal biopsy, which is a lot less invasive than a brain biopsy, to make a diagnosis," says Dr. Kenneth Tyler, author of a "perspective" article that accompanies the study in the Feb. 20 issue of The New England Journal of Medicine.
CJD is the most common of a family of human and animal diseases called transmissible spongiform encephalopathies. This form of the disease is extremely rare, affecting only one in 1 million people worldwide each year.
There are three forms of Creutzfeldt-Jakob disease. The most common, accounting for about 85 percent of all cases, is "sporadic," meaning there is no apparent cause. There is also a genetic variety and iatrogenic forms. The latter is transmitted by contact with brain or nervous system tissue, usually during a medical procedure. Contaminated instruments may play a role in these transmissions.
All forms of the disease appear to be caused by a protein called a prion. Normal prions are present in the human body and are harmless. When the prions fold into a different shape, however, they acquire a more lethal character.
The authors of this study looked at nine patients in the Veneto region of Italy who had died of sporadic CJD, which was confirmed by autopsies.
The telltale prion was found in all nine patients in the area of the nose that processes the sense of smell; it was not found in tissue samples from 11 controls.
In these nine cases, the prion was present in the nasal areas relatively early in the course of the disease, raising questions about the route of infection. Specifically, how and when did it get there?
One possibility is that it traveled inside out, from the brain through the various nerve connections, Tyler says.
"It's entirely possible that the infection gets to the brain through some other pathway and just happens to reach these nerve cells that are involved in smell and olfaction," Tyler says. "It may have nothing whatsoever to do with how the virus gets in."
On the other hand, this collection of olfactory nerve cells are relatively unique in that they are partially exposed to the outside environment.
"There really aren't any other nerve cells quite like that in the body," Tyler says. "So one of the questions would be, 'Is it possible that this could also be a route of entry for these agents into the nervous system?'"
There have been other, rare cases when the olfactory system was involved in transmitting a viruses. For instance, the rabies virus has been found in people who were spelunking in caves filled with rabid bats, Tyler says.
As of yet, however, there's no evidence that CJD can be transmitted from person to person.
For the prion to work as a diagnostic test, it needs to be both sensitive -- meaning it has to be present in a high percentage of people who have the disease -- and specific - meaning it's not present in other diseases.
While there's currently no cure for CJD, a diagnostic test could be beneficial for clinical trials. Experimental research is looking into ways of dissolving these clusters of abnormal proteins in animal and lab models.
Should these methods have any chance of succeeding in humans, you'd need to be able to diagnose the disease quickly and accurately in study participants, Tyler says.
"Otherwise, you may be treating people who don't even have the disease, which can really confound your results," he adds. "And it's a little bit tough if you have to have to wait till somebody dies."
More information
For more on CJD, visit the Creutzfeldt-Jakob Disease Foundation or the National Institute of Neurological Disorders and Stroke
