![]() On a mini-mental state examination, she scored abnormally low in the measure of attention and calculation and she had reduced ability to repeat the names of three unrelated objects. In June 2006, she demonstrated anisocoria and bizarre behavior, including talking incoherently to herself, and she was then referred to psychiatry. (Table 1) Based on the medical record and her neurologist, her illness began in August 2005 with attention deficits and progressive memory loss. ![]() In February 2007, the Centers for Disease Control and Prevention (CDC) and the National Prion Disease Pathology Surveillance Center (NPDPSC) notified the Texas Department of State Health Services (DSHS) of a 32-year-old woman with an 18-month history of progressive neurological symptoms suggestive of CJD. To make clinicians more aware of an unusual presentation of prion disease and to demonstrate the importance of pursuing a thorough sleep history when prion disease is being considered, we describe the clinical and pathological details of a patient whose sFI diagnosis had not been considered antemortem. The rarity of the disease can make the diagnosis of sFI challenging. Because the patients are deprived of sleep they may display drowsiness during the day which may be described as hypersomnolence unless the abnormal nocturnal sleep pattern is recognized by electroencephalogram (EEG) and/or polysomnography (PSG). Other clinical features consist of peculiar behaviors that can be mistaken for psychotic signs. Like FFI, sFI is characterized pathologically by thalamic atrophy and clinically by disrupted sleep, autonomic dysfunction, and motor abnormalities including myoclonus, ataxia, dysarthria, dysphagia, and pyramidal signs. An additional ten patients have been reported in the literature as sFI, expanding the age range to 30-74 and the disease duration to 13-73 months. Parchi and colleagues reported five such cases in subjects between the ages of 36 and 70 years (mean 50) with duration of illness ranging from 15 to 24 months (mean 17.8). Īlthough Kawasaki and colleagues described a probable case of sFI in 1997, the disease was definitively established in 1999 by both Mastrianni et al and Parchi et al utilizing the term sporadic fatal insomnia. sFI lacks the D178N PRNP mutation but appears to be invariably associated with methionine homozygosity at codon 129 of the PRNP, suggesting that 129M, either coupled with the D178N mutation or present in both alleles in the absence of the mutation is a requirement for the phenotypic expression of fatal insomnia. ![]() The presence of valine at codon 129 (129V) coupled with the same D178N mutation is associated with a very different phenotype reminiscent of CJD. FFI is linked to the presence of a D (aspartic acid) to N (asparagine) variation at codon 178 (D178N) coupled with the methionine at codon 129 (129M) on the mutant allele of the prion protein gene ( PRNP). sFI shares a very similar phenotype to FFI, but is not associated with a mutation in the prion protein gene. Genetic or familial cases are linked to a mutation on the prion protein gene, and include several subtypes of Gerstmann Sträussler Scheinker syndrome, familial CJD, and fatal familial insomnia (FFI). Acquired cases include iatrogenic CJD, acquired by medical or surgical procedures, and variant CJD, usually acquired from consuming beef products contaminated with the agent of bovine spongiform encephalopathy. Sporadic cases, with no known environmental source of infection, include sporadic Creutzfeldt - Jakob disease (CJD), the most common human prion disease, and sporadic fatal insomnia (sFI), one of the least common. They are classified into three main groups: sporadic, acquired, and genetic. Human prion diseases are rare, transmissible, invariably fatal neurodegenerative diseases that are characterized by the accumulation of a misfolded host protein, the prion protein, in brain tissue. In patients with suspected prion disease, a characteristic change in sleep pattern can be an important clinical clue for identifying sFI or FFI polysomnography (PSG), genetic analysis, and nuclear imaging may aid in diagnosis. Genetic tests identified no prion protein (PrP) gene mutation, but neuropathological examination and molecular study showed protease-resistant PrP (PrP res) in several brain regions and severe atrophy of the anterior-ventral and medial-dorsal thalamic nuclei similar to that described in FFI. Following death of this patient, an interview with a close family member indicated the patient's illness included a major change in her sleep pattern, corroborating the reported autopsy diagnosis of sFI. We report a case of a 33-year-old female who died of a prion disease for whom the diagnosis of sFI or FFI was not considered clinically. Sporadic fatal insomnia (sFI) and fatal familial insomnia (FFI) are rare human prion diseases.
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