What happens in Creutzfeldt-Jakob disease, exactly?

What is it?

Creutzfeldt-Jakob disease or CJD is a neurodegenerative disease, which means that it progressively leads to the destruction of the nervous system and its functions. It is incurable, able of transmission,  and leads to death.

CJD occurs at a rate of about 1 case a year in 1 000 000 people. It is most common in people aged 60-65. On average, CJD leads to death after 4 months of the appearance of symptoms, but lifespans much longer or shorter than this are not infrequent.

The first symptom of CJD is a rapidly progressing dementia. The affected suffer from impairments in memory, judgment, thought, vision, and muscular coordination. Psychological symptoms such as depression, anxiety, hallucinations, and obsessive-compulsory behavior are common. Later in the illness mental problems become severe, and the sufferer might go blind and experience involuntary jerky movements. Eventually they loose the ability to move and speak, and enter a coma. There are a few different forms of CJD, and the symptoms show some variation between them.

What causes it?

CJD is caused by a protein called prion. Prions are very common in the cells of the central nervous system: the CJD form has the same building blocks in the same order as the normal form, but the CJD form has been folded differently. This misfolded prion then causes a chain reaction in the surrounding proteins, turning them into the CJD form.

About 85% of CJD cases are sporadic. They are thought to occur because some of a persons normal prion proteins spontaneously turn into the CJD conformation and start a chain reaction. About 5-10% of CJD cases are hereditary, and caused by a mutation in the gene that codes the normal prion protein. CJD can also be acquired by eating or being in some other way exposed to tissue (human or animal) contaminated by faulty prions.

What happens during it? 

The CJD associated prion protein appears on cell surfaces and is thought to play a role in adhesion and signaling. Breaking proteins down is a normal process in the cell, taking place if there’s too much of a protein or it is no longer needed. Enzymes called proteases are specialized in doing this. When the CJD prion is abnormally folded, however, the enzymes are no longer able to attach to it and break it down. This causes the misfolded prions to precipitate as insoluble tangles called amyloids, which accumulate inside the brain and cause neurons to die through processes not thoroughly understood. Research indicates that cell death might be caused by the activation of a “death receptor”: a receptor that leads the cell to kill itself when it receives a message. The brains of those with CJD start to resemble sponges, because neurons die in groups leaving holes around the brain.

How can it be treated?

There is no cure for CJD. One experimental medication (pentosan polysulphate) is possibly able to slow down the progression of the disease and to postpone death with a few years, but sufficient evidence doesn’t exist to support any claims of the effectiveness of the medication. Research on other cures is conducted all the time and some promising results have been achieved, though study on these alternatives is still in progress.

Current treatment is based on minimizing uncomfort. Opiates can be used to alleviate pain, and other drugs can be used to reduce the involuntary movements. During the later stages when the affected is unable to move, their position should be frequently changed, and draining urine with a catheter and using artificial feeding can also be useful.

 

Sources: http://www.ninds.nih.gov/disorders/cjd/detail_cjd.htm#3058_9, http://emedicine.medscape.com/article/1168941-overview, http://neuropathology-web.org/chapter5/chapter5ePrions.html, http://www.ncbi.nlm.nih.gov/pubmed/12879983, https://en.wikipedia.org/wiki/Creutzfeldt–Jakob_disease

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