Creutzfeldt-Jakob disease (CJD) is a rare, but deadly degenerative, transmissible, and rapidly progressive disease of the brain. CJD is also known as a neurocognitive disorder due to prion disease. Encephalopathy is a disease in which the functioning of the brain is affected. CJD fits into a family of deadly degenerative disorders of the nervous system that are called transmissible spongiform encephalopathies or prion diseases.
CJD leads to rapidly progressive dementia and can incubate asymptomatically for decades in humans before becoming clinically noticeable. CJD is caused by an infectious agent termed ‘prion’, which is a pathologic misfolded modification of the prion protein or PrP, an endogenous cellular protein. Over 90% of patients die within a year of onset of symptoms from CJD, which occurs sporadically. The distinctive feature of CJD is the degeneration of the brain, especially the reduction in cortical thickness, which is most frequently observed within the frontal, temporal, and parietal lobes of the brain. Most CJD cases arise sporadically (sCJD) for no definitive reason, genetic or inherited and acquired forms of CJD also occur. There is further another significantly transmissible classification of CJD namely variant CJD (vCJD) which devastated the U.K population two decades ago.
In 2000, the vCJD epidemic remained at a peak in the UK with 28 deaths but subsequently declined. The annual number of confirmed cases of clinical vCJD has continued to decline globally since 2005. In contrast to sCJD, vCJD occurs at a younger age with a mean age of onset of 26 years and has a longer median clinical manifestation time of approximately 1 year. Iatrogenic CJD or iCJD is still a potential acquired public health threat, though no epidemics have been reported over the last five years. Another rare CJD manifestation is called iatrogenic CJD or iCJD.
CJD presents with rapidly progressing dementia, cerebellar and extrapyramidal signs (related to movement impairment), myoclonus or sudden brief involuntary jerking of muscles, and visual disturbances ranging from impaired vision to blindness. Symptomatically, individuals initially experience muscle coordination problems, changes in personality comprising impaired memory, thinking, and judgment capacity, and impaired vision. As the illness advances, the mental state worsens, involuntary muscle jerks develop, and complete blindness may ensue. Subsequently, the patients with CJD can even lose the ability to speak and move. The ultimate stage for patients is in a coma. Pneumonia frequently occurs in affected individuals which alone can be fatal.
The clinical manifestations of sCJD are rapid cognitive decline, damage in the part of the cerebellum of the brain, and myoclonus resulting in a mute state. The diagnosis of CJD is reliant on the assessment of clinical features as well as laboratory-based analysis. Changes have been made in the formal diagnostic criteria for sCJD mentioned in the European Union or EU based on advanced diagnostic techniques and protocols. For further confirmatory assessment, the following diagnostic procedures are employed:
Magnetic resonance imaging or MRI is the most beneficial modality in detecting cases of CJD because it is non-invasive, highly sensitive, and specific in detecting both sCJD and vCJD cases.
Real-time quaking-induced conversion (RT-QuIC) is a comparatively novel CSF-based test. This procedure has shown extraordinarily high sensitivity and specificity in recent studies in patients with sCJD as well as the genetic form of CJD.
Some diagnostically useful cerebrospinal fluid (CSF) biomarkers, such as S100b, 14-3-3, and tau, are useful in detecting patients with CJD.
Investigators are now using protein misfolding cyclic amplification or PMCA technique, similar conceptually to a polymerase chain reaction (PCR), but does not use nucleotides, to detect the abnormal PrPSc protein, which is also insoluble and misfolded.
The electroencephalogram (EEG) diagnostic technique has become a less useful tool given the advent of MRI and CSF tests, nonetheless, it remains a significant non-invasive test for many sCJD patients. In vCJD patients, PrPSc can also be detected in biopsies taken from tonsils by basic methods of immunoblotting and immunohistochemistry.
Currently, there is no cure for CJDs. Treatment includes giving symptomatic relief to patients with pain, anxiety, depression, muscle jerks, and tremors. Psychological symptoms such as anxiety and depression can be managed with sedatives and antidepressants, while tremors can be managed by drugs like clonazepam and sodium valproate. Pain can be mitigated by powerful opiate-based painkillers.
Being a contagious disease, future management should involve the early detection and isolation of CJD patients from the community in order to stop the chain of transmission. Further management of such patients should always be employed under biosafety level containments.