FFI is also invariably linked to the presence of the methionine codon at position 129 of the mutant allele, whereas fCJD is linked to the presence of the valine codon at that position. "The disease is where there is a change of amino acid at position 178 when an asparagine (N) is found instead of the normal aspartic acid (D). This has to be accompanied with a methionine at position 129." Pathophysiology
In itself, the presence of prions causes reduced glucose use by the thalamus and a mild hypo-metabolism of the cingulate cortex. The extent of this symptom varies between two variations of the disease, these being those presenting methionine homozygotes at codon 129 and methionine/valine heterozygotes being the most severe in the latter one. Given the relationship between the involvement of the thalamus in regulating sleep and alertness, a causal relationship can be drawn, and is often mentioned as the cause. Diagnosis
Diagnosis is suspected based on symptoms. Further work up often include a sleep study and PET scan. Confirmation of the familial form is by genetic testing. Differential diagnosis
Other diseases involving the mammalian prion protein are known. Some are transmissible (TSEs, including FFI) such as kuru, bovine spongiform encephalopathy (BSE, also known as "mad cow disease") in cattle, and chronic wasting disease in American deer and American elk in some areas of the United States and Canada, as well as Creutzfeldt–Jakob disease (CJD).
Fatal familial insomnia is an extremely rare genetic (and even more rarely, sporadic) disorder that results in trouble sleeping as its hallmark symptom. The problems with sleeping typically start out gradually and worsen over time. Other symptoms may include speech problems, coordination problems, and dementia. It results in death within a few months to a few years.Fatal familial insomnia is a prion disease of the brain. It is usually caused by a mutation to the gene encoding protein PrPC. It has two forms: fatal familial insomnia (FFI), which is autosomal dominant, and sporadic fatal insomnia (sFI), which lacks the gene mutation. Diagnosis is suspected based on symptoms and can be supported by a sleep study, a PET scan, and genetic testing if the patients family has a history of the disease. Similar to other prion diseases, the diagnosis can only be confirmed by a brain autopsy at post-mortem.Fatal insomnia has no known cure and involves progressively worsening insomnia, which leads to hallucinations, delirium, and confusional states like that of dementia, until the patient slips into a stupor and eventually dies. The average survival time from onset of symptoms is 18 months. The first recorded case was an Italian man who died in Venice in 1765. Signs and symptoms
The disease has four stages:
Characterized by worsening insomnia, resulting in panic attacks, paranoia, and phobias. This stage lasts for about four months. Hallucinations and panic attacks become noticeable, continuing for about five months. Complete inability to sleep is followed by rapid loss of weight.