Creutzfeldt-Jakob disease with PRNP G114V mutation in a Chinese family

A longitudinal 18F-FDG PET/MRI study in asymptomatic stage of genetic Creutzfeldt-Jakob disease linked to G114V mutation

BACKGROUND

Pathogenic prion protein may start to deposit in some brain regions and cause functional alterations in the asymptomatic stage in Creutzfeldt-Jakob disease. The study aims to determine the trajectory of the brain metabolic changes for prion protein diseases at the preclinical stage.

METHODS

At baseline, we enrolled five asymptomatic PRNP G114V mutation carriers, six affected genetic PRNP E200K CJD patients and 23 normal controls. All participants completed clinical, diffusion-weighted imaging (DWI) and ¹⁸F fluorodeoxyglucose-positron emission tomography (¹⁸F-FDG-PET) examinations. Longitudinal follow-up was completed in five asymptomatic mutation carriers. We set three-time points to identify the changing trajectory in the asymptomatic carriers group including baseline, 2-year and 4-year follow-up.

RESULTS

At baseline, DWI signals, the cerebral glucose standardized uptake value rate ratio (SUVR) and clinical status in 5 asymptomatic cases were normal. At the follow-up period, mild hypometabolism on PET images was found in asymptomatic carriers without any DWI abnormal signal. Further group quantitatively analysis showed hypometabolic brain regions in the asymptomatic genetic CJD group were in the insula, frontal, parietal, and temporal lobes in 4-year follow-up. The SUVR changing trajectories of all asymptomatic cases were within the range between the normal controls and affected patients. Notably, the SUVR of one asymptomatic individual whose baseline age was older showed a rapid decline at the last follow-up.

CONCLUSIONS

Our study illustrates that the neurodegenerative process associated with genetic CJD may initiate before the clinical presentation of the disease.

Case Report: Genetic Creutzfeldt–Jakob Disease With a G114V Mutation and One Octapeptide Repeat Deletion as a Mimic of Frontotemporal Dementia

Genetic Creutzfeldt–Jakob disease (gCJD) characterized by mutations in the prion protein (PrP) gene (PRNP) contributes to approximately 10–15% of the overall human prion diseases. Here, we report a rare mutation in the PRNP gene in a Han-Chinese family. A 36-year-old man initiated with anxiety and depression followed by progressive dementia, cogwheel-like rigidity combined with tremors, and he was diagnosed with frontotemporal lobar dementia in the first 2 years. The disease progression was relatively slow, and the patient developed into akinetic mutism in 4 years. To characterize the disease, following the pedigree studies, neuropsychological examination, neuroimaging studies, real-time quaking-induced conversion (RT-QuIC) examination, and so on were conducted. We eventually identified a rare mutation of G114V combined with one octapeptide repeats deletion (1-ORPD) in the PrP in the patient by DNA sequencing. In addition, the same mutation and deletion were subsequently identified in the patient's mother without any syndromes. His maternal grandmother had a late onset of the disease in her 60s. Given that 1-OPRD has never been reported in human prion disease before, our first report that both G114V mutation and 1-OPRD appear in the family would forward our understanding of the etiological mechanisms of the gCJD.

White Matter Integrity Involvement in the Preclinical Stage of Familial Creutzfeldt-Jakob Disease: A Diffusion Tensor Imaging Study

Objective

The objective of the study was to explore patterns of white matter (WM) alteration in preclinical stage familial Creutzfeldt–Jakob disease (fCJD) using diffusion tensor imaging (DTI).

Methods

Seven asymptomatic carriers of the PRNP G114V mutation and six non-carriers were recruited from the same fCJD kindred and follow-up obtained from all asymptomatic carriers and two non-carriers 2 years later. Overlapping WM patterns were also explored in asymptomatic carriers and symptomatic CJD patients. All participants underwent clinical and neuropsychological assessments and DTI at baseline and follow-up. DTI data were subjected to whole-brain voxel-wise analysis of fractional anisotropy (FA) and mean diffusivity (MD) in WM using tract-based spatial statistics. Three comparisons were conducted: baseline carriers against non-carriers (baseline analysis), changes after 2 years in carriers (follow-up analysis), and differences between patients with symptomatic CJD and healthy controls (CJD patient analysis).

Results

Neither carriers nor non-carriers developed any neurological symptoms during 2 years of follow-up. Baseline analysis showed no differences between the carrier and non-carrier groups in MD and FA. Follow-up analysis showed significantly increased MD in multiple WM tracts, among which increased MD in the bilateral superior longitudinal fasciculus, bilateral anterior thalamic radiation, bilateral cingulate gyrus, and left uncinate fasciculus overlapped the patterns observed in patients with symptomatic CJD.

Conclusion

Changes in integrity within multiple WM tracts can be detected during the preclinical stage of fCJD.

First European case of Creutzfeldt-Jakob disease with a PRNP G114V mutation

Genetic Creutzfeldt-Jakob disease is due to mutations in the PRNP gene. Only two families with a PRNP G114V mutation have been described around the world. We report the first European case, who had no family history and initially presented with isolated deficit in hippocampus-dependent memory. Initial investigations were normal except for elevated total tau protein in the cerebrospinal fluid. He died 4 years after disease onset. This case highlights the diagnostic difficulties posed by genetic Creutzfeldt-Jakob disease, and shows that genetic analyses should be considered even in sporadic cases.

Genetic PrP Prion Diseases

Genetic prion diseases (gPrDs) caused by mutations in the prion protein gene (PRNP) have been classified as genetic Creutzfeldt-Jakob disease, Gerstmann-Sträussler-Scheinker disease, or fatal familial insomnia. Mutations in PRNP can be missense, nonsense, and/or octapeptide repeat insertions or, possibly, deletions. These mutations can produce diverse clinical features. They may also show varying ancillary testing results and neuropathological findings. Although the majority of gPrDs have a rapid progression with a short survival time of a few months, many also present as ataxic or parkinsonian disorders, which have a slower decline over a few to several years. A few very rare mutations manifest as neuropsychiatric disorders, with systemic symptoms that include gastrointestinal disorders and neuropathy; these forms can progress over years to decades. In this review, we classify gPrDs as rapid, slow, or mixed types based on their typical rate of progression and duration, and we review the broad spectrum of phenotypes manifested by these diseases.

Genetic Creutzfeldt-Jakob disease

Genetic Creutzfeldt-Jakob disease (CJD) is associated with mutations in the human PrP gene (PRNP) on chromosome 20p12-pter. Pathogenic mutations have been identified in 10-15% of all CJD patients, who often have a family history of autosomal-dominant pattern of inheritance and variable penetrance. However, the use of genetic tests implemented by surveillance networks all over the world increasingly identifies unexpectedly PRNP mutations in persons apparently presenting with a sporadic form of CJD. A high phenotypic variability was reported in genetic prion diseases, which partly overlap with the features of sporadic CJD. Here we review recent advances on the epidemiologic, clinical, and neuropathologic features of cases that phenotypically resemble CJD linked to point and insert mutations of the PRNP gene. Multidisciplinary studies are still required to understand the phenotypic spectrum, penetrance, and significance of PRNP mutations.

Genetic prion disease: Experience of a rapidly progressive dementia center in the United States and a review of the literature

Although prion diseases are generally thought to present as rapidly progressive dementias with survival of only a few months, the phenotypic spectrum for genetic prion diseases (gPrDs) is much broader. The majority have a rapid decline with short survival, but many patients with gPrDs present as slowly progressive ataxic or parkinsonian disorders with progression over a few to several years. A few very rare mutations even present as neuropsychiatric disorders, sometimes with systemic symptoms such as gastrointestinal disorders and neuropathy, progressing over years to decades. gPrDs are caused by mutations in the prion protein gene (PRNP), and have been historically classified based on their clinicopathological features as genetic Jakob-Creutzfeldt disease (gJCD), Gerstmann-Sträussler-Scheinker (GSS), or Fatal Familial Insomnia (FFI). Mutations in PRNP can be missense, nonsense, and octapeptide repeat insertions or a deletion, and present with diverse clinical features, sensitivities of ancillary testing, and neuropathological findings. We present the UCSF gPrD cohort, including 129 symptomatic patients referred to and/or seen at UCSF between 2001 and 2016, and compare the clinical features of the gPrDs from 22 mutations identified in our cohort with data from the literature, as well as perform a literature review on most other mutations not represented in our cohort. E200K is the most common mutation worldwide, is associated with gJCD, and was the most common in the UCSF cohort. Among the GSS-associated mutations, P102L is the most commonly reported and was also the most common at UCSF. We also had several octapeptide repeat insertions (OPRI), a rare nonsense mutation (Q160X), and three novel mutations (K194E, E200G, and A224V) in our UCSF cohort. © 2016 Wiley Periodicals, Inc.

Quantifying prion disease penetrance using large population control cohorts

More than 100,000 genetic variants are reported to cause Mendelian disease in humans, but the penetrance-the probability that a carrier of the purported disease-causing genotype will indeed develop the disease-is generally unknown. We assess the impact of variants in the prion protein gene (PRNP) on the risk of prion disease by analyzing 16,025 prion disease cases, 60,706 population control exomes, and 531,575 individuals genotyped by 23andMe Inc. We show that missense variants in PRNP previously reported to be pathogenic are at least 30 times more common in the population than expected on the basis of genetic prion disease prevalence. Although some of this excess can be attributed to benign variants falsely assigned as pathogenic, other variants have genuine effects on disease susceptibility but confer lifetime risks ranging from <0.1 to ~100%. We also show that truncating variants in PRNP have position-dependent effects, with true loss-of-function alleles found in healthy older individuals, a finding that supports the safety of therapeutic suppression of prion protein expression.

Pathogenic mutations within the hydrophobic domain of the prion protein lead to the formation of protease-sensitive prion species with increased lethality

Prion diseases are a group of fatal and incurable neurodegenerative diseases affecting both humans and animals. The principal mechanism of these diseases involves the misfolding the host-encoded cellular prion protein, PrP(C), into the disease-associated isoform, PrP(Sc). Familial forms of human prion disease include those associated with the mutations G114V and A117V, which lie in the hydrophobic domain of PrP. Here we have studied the murine homologues (G113V and A116V) of these mutations using cell-based and animal models of prion infection. Under normal circumstances, the mutant forms of PrP(C) share similar processing, cellular localization, and physicochemical properties with wild-type mouse PrP (MoPrP). However, upon exposure of susceptible cell lines expressing these mutants to infectious prions, very low levels of protease-resistant aggregated PrP(Sc) are formed. Subsequent mouse bioassay revealed high levels of infectivity present in these cells. Thus, these mutations appear to limit the formation of aggregated PrP(Sc), giving rise to the accumulation of a relatively soluble, protease sensitive, prion species that is highly neurotoxic. Given that these mutations lie next to the glycine-rich region of PrP that can abrogate prion infection, these findings provide further support for small, protease-sensitive prion species having a significant role in the progression of prion disease and that the hydrophobic domain is an important determinant of PrP conversion.

IMPORTANCE

Prion diseases are transmissible neurodegenerative diseases associated with an infectious agent called a prion. Prions are comprised of an abnormally folded form of the prion protein (PrP) that is normally resistant to enzymes called proteases. In humans, prion disease can occur in individuals who inherited mutations in the prion protein gene. Here we have studied the effects of two of these mutations and show that they influence the properties of the prions that can be formed. We show that the mutants make highly infectious prions that are more sensitive to protease treatment. This study highlights a certain region of the prion protein as being involved in this effect and demonstrates that prions are not always resistant to protease treatment.

Creutzfeldt-Jakob disease cluster in the health area of Meixoeiro Hospital

OBJECTIVE

Galicia is the Spanish region in which most bovine spongiform encephalopathy cases have been registered. Meixoeiro Hospital is included in the Galician Health Service (SERGAS). The aim of the study was to analyze the clinical and epidemiological characteristics of Creutzfeldt-Jakob disease (CJD) in the health area of Meixoeiro Hospital and to identify possible specific risk factors to the general public.

METHODS

All incident cases of CJD were identified in the health area of Meixoeiro Hospital (187,877 inhabitants) over a 14-year period, 1997-2010, and classified according to WHO diagnostic criteria. We obtained clinical detail and epidemiological information on all cases. Crude and age-specific incidence rates were calculated. A review of surgical or invasive medical procedures was undertaken.

RESULTS

We diagnosed 12 patients with CJD, 10 sporadic CJD (sCJD), and two genetic CJD (gCJD). No iatrogenic or variant CJD was detected. According to Poisson distribution, 3.9 CJD cases would be expected for our area over the 14 years researched. The average yearly mortality rate from CJD was 4.6 cases per million (3.8 from sCJD and 0.8 from gCJD). Eight patients (67%) underwent at least one surgical or invasive medical procedure. Sixteen of twenty-seven (59%) of these procedures were undertaken in Meixoeiro Hospital.

CONCLUSIONS

The incidence of CJD in the health area of Meixoeiro Hospital is three times higher than expected. The hypothesis that at least some cases of sCJD are apparently because of covert transmission or zoonosis events should not be formally refuted and might explain the high rate found.

Imaging of prion diseases

Prion diseases are caused by self-replicating proteins that induce lethal neurodegenerative disorders. In the last decade, the understanding of the different clinical, pathological, and neuroimaging phenotypes of this group of disorders has evolved paralleling the advances in prion molecular biology. From an imaging standpoint, the implementation of diffusion-weighted imaging in routine practice has markedly facilitated the detection of prion diseases, especially Creutzfeldt-Jakob. Less frequent prion-related disorders, including genetic diseases, may also benefit from progresses in the field of quantitative diffusion-weighted imaging, MR spectroscopy or molecular imaging. Herein, we present a review of the neuroimaging features of the prion disorders known to affect humans emphasizing the important contribution of MRI in the diagnosis of this group of disorders.

Genetic Creutzfeldt-Jakob disease and fatal familial insomnia: insights into phenotypic variability and disease pathogenesis

Human prion diseases are a group of rare neurodegenerative disorders characterized by the conversion of the constitutively expressed prion protein, PrP(C), into an abnormally aggregated isoform, called PrP(Sc). While most people who develop a prion disease have no identifiable cause and a few acquire the disease through an identified source of infection, about 10-15% of patients are affected by a genetic form and carry either a point mutation or an insertion of octapeptide repeats in the prion protein gene. Prion diseases show the highest extent of phenotypic heterogeneity among neurodegenerative disorders and comprise three major disease entities with variable though overlapping phenotypic features: Creutzfeldt-Jakob disease (CJD), fatal insomnia and the Gerstmann-Sträussler-Scheinker syndrome. Both CJD and fatal insomnia are fully transmissible diseases, a feature that led to the isolation and characterization of different strains of the agent or prion showing distinctive clinical and neuropathological features after transmission to syngenic animals. Here, we review the current knowledge of the effects of the pathogenic mutations linked to genetic CJD and fatal familial insomnia on the prion protein metabolism and physicochemical properties, the disease phenotype and the strain characteristics. The data derived from studies in vitro and from those using cell and animal models are compared with those obtained from the analyses of the naturally occurring disease. The extent of phenotypic variation in genetic prion disease is analyzed in comparison to that of the sporadic disease, which has recently been the topic of a systematic and detailed characterization.