Creutzfeldt-Jakob disease is a fatally degenerative brain disease that is, thankfully, pretty rare but is also extremely hard to diagnose conclusively. The only truly definitive way to diagnose is a brain biopsy after death. That may be changing, at least in the cases that have developed from corneal implants.
CJD belongs to a group of diseases that affect humans and animals called transmissible spongiform encephalopathies (TSE). This group includes kuru, fatal familial insomnia, and Gerstmann-Straussler-Scheinker disease (GSS) in humans and scrapie, chronic wasting disease, and Mad Cow (bovine spongiform encephalopathy) in other animals. In cases of this disease the brain tissue begins to become filled with holes until they begin to resemble a sponge when it is examined under a microscope. This damage causes all manners of neurological problems such as dementia, insomnia, depression, muscle coordination problems, and personality changes. As the disease progresses, mental impairment becomes severe. CJD has many symptoms similar to Parkinson’s’ and Huntington’s’ diseases but the progression is much quicker and the change in brain tissue is unique.
All of these diseases are caused by a pesky little protein called a prion. (Prion – the combination of the words protein and infectious and first coined by Stanley B. Prusiner of the University of California School of Medicine in San Francisco in 1982.) A prion is a strange infectious agent unlike anything else scientists had seen in that it has no nucleic acid genome that has adopted an abnormal form. All previously known infectious agents such as bacteria and viruses have nucleic acids which helps them reproduce. It is the buildup of these prions that causes the damage to brain tissue.
There are three different categories of CJD: sporadic, the disease appears even though the patient has no risk factors for it; hereditary, the patient has a familial history of the disease and a positive test result for the genetic mutation; and acquired, the disease is transmitted through contaminated brain and/or nerve tissue, usually through a medical procedure. The possibility of developing this disease is indeed a scary thing but it is still a relatively rare occurrence and at least one type may now be easier to diagnose.
National Institute of Health researchers have found evidence of the infectious agent of the sporadic type in the eyes of CJD patients. These findings may suggest an avenue of early CJD diagnosis but may also raise some questions in regards to routine eye exams and corneal transplants. Researchers from the National Institute of Allergy and Infectious Diseases (NIAID), UC San Diego, and UC San Francisco are currently collaborating in their investigations and hope that early diagnosis of sporadic CJD and related diseases such as Parkinson’s, Alzheimer’s, and dementia with Lewy bodies might lead to effective treatments and prevention.
Almost 40% of all sporadic CJD patients develop eye problems sending them for eye exams meaning that the potential for the spreading of infection is real. Furthermore, cadaveric corneal transplants from donors with undiagnosed CJD are a possibility and scientists believe have led to two or three possible cases. Previously it was believed that prions might be present in eye tissue but a recent study of 11 deceased CJD patients showed these prions present in all 11 cases. Scientists are using a very sensitive test called real time quake-inducing conversion (RT-QuIC) that can detect prion seeding activity within the eye and can be used in a clinical setting.
There are also plans to use the RT-QuIC test to evaluate the eyes of patients with Parkinson’s, Alzheimer’s, and dementia with Lewy bodies to determine if there is a presence of infectious proteins from those diseases. Any new information discovered about these diseases and the possibility of detecting them earlier can only benefit those afflicted.
–Janice Willson
References:
https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Fact-Sheets/Creutzfeldt-Jakob-Disease-Fact-Sheet
https://mbio.asm.org/content/9/6/e02095-18
Photo Source: Laitr Keiows
