Clinical Neuroscience

[GENETIC BACKGROUND OF HUMAN PRION DISEASES]

KOVÁCS Gábor Géza1

NOVEMBER 30, 2007

Clinical Neuroscience - 2007;60(11-12)

[acquired. The human prion protein gene (PRNP) is located to chromosome 20 (20p12-ter). Mutations and polymorphisms in the PRNP are associated with prion disease. Genetic prion diseases are inherited in an autosomal dominant trait, examination of the penetrance is restricted to mutation E200K (59-89%). Mutations can be substitutions or insertions. Genetic prion diseases are classified according to the clinicopathological phenotype and comprise genetic Creutzfeldt-Jakob disease, Gerstmann-Sträussler-Scheinker disease and fatal familial insomnia. Base pair insertions may resemble Creutzfeldt-Jakob disease or Gerstmann-Sträussler-Scheinker disease phenotypes, however, their unique clinicopathological presentations are also emphasized. Among the polymorphisms of the PRNP, the one at codon 129 is the most important, where methionine or valine may be encoded. This polymorphism is known to influence the phenotype of disease forms. Molecular classification of sporadic Creutzfeldt-Jakob disease also depends on the codon 129 polymorphisms in addition to the Western blot pattern of the protease resistant prion protein. According to this at least six well characterised forms of sporadic Creutzfeldt-Jakob disease are known. Influence of other genes were also investigated. Contrasting results are reported regarding the role of apolipoprotein E allele ε4, but presence of allele ε2 seems to influence the prognosis. Polymorphisms in the doppel gene or ADAM10 could not be clearly associated with Creutzfeldt-Jakob disease. Polymorphisms in the upstream and intronic regulatory region of the PRNP gene may be a risk factor for Creutzfeldt-Jakob disease. The PRNP codon 129 polymorphism was examined in non-prion diseases. Some studies suggest that this polymorphism may have influence on the cognitive decline and early onset Alzheimer’s disease.]

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  1. Institute of Neurology, Medical University of Vienna, Vienna

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[One-and-a-half syndrome is characterized by combination of the clinical features of unilateral horizontal gaze palsy and internuclear ophthalmoplegia. The common symptoms are double vision and oscillopsia. The lesion is located in the paramedian pontine reticular formation, involving the centre of horizontal gaze and medial longitudinal fasciculus. More extensive brainstem damage may result in additional neurological signs. The most frequent underlying diseases are vascular insults, multiple sclerosis, and brainstem tumor. We present two cases of one-and-a-half syndrome. Both patients had lacunar infarction in the paramedian pontine tegmentum, revealed by MRI. The first patient had isolated eye movement disorder, while the second had additional nuclear-type facial paresis. In the first case brainstem evoked potentials indicated brainstem damage, in the second patient it was normal. Ocular symptoms improved within some days in both patients.]

Clinical Neuroscience

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[Background - Sporadic Creutzfeldt-Jakob disease is the most frequent human prion disease. Genetic forms are associated with mutations in the human prion protein gene (PRNP) and thought to comprise 5-15% of cases. Acquired forms include iatrogenic and variant Creutzfeldt-Jakob disease. The latter is associated with the bovine spongiform encephalopathy. We recently reported the high incidence of genetic Creutzfeldt-Jakob disease in Hungary. Materials and methods - In the present study we summarize the results of a widened investigation comprising Creutzfeldt-Jakob disease cases collected in the National Institute of Psychiatry and Neurology, Hungary in the last 12 years. We examined the disease forms and their geographical distribution. Results - Our study involved 155 patients. The four major results are as follows: 1. In Hungary we detected only sporadic and genetic forms of human prion disease, while iatrogenic and variant Creutzfeldt-Jakob disease were not observed. 2. The proportion of genetic prion disease (E200K mutation), similarly to Slovakia, is higher than reported worldwide. Our observations indicate that at least every third case is genetic Creutzfeldt-Jakob disease. The mean incidence of genetic Creutzfeldt-Jakob disease (0.42/million) is unusually high. Especially the year 2006 was striking when the incidence of genetic Creutzfeldt-Jakob disease was 1.4/million. 3. More than half of genetic Creutzfeldt-Jakob disease cases lack a positive family history. 4. Some counties and the eastern part of Hungary shows elevated incidence of human prion disease. Conclusions - Differences in the geographical distribution may be related to migration and historical relationship with the Slovakian population. Based on the increased incidence of E200K mutation, genetic testing of the PRNP is recommended in all cases with atypical neuropsychiatric disorder or suspicion of prion disease.]

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