Clinical Features

The average age of onset is 45 to 75 years, but it may occur earlier or later. Rapidly progressing dementia; myoclonus; combinations of cerebellar, pyramidal, extrapyramidal, and sensory symptoms and signs; and seizures characterize the clinical picture. The course is short; the patient is eventually in a vegetative state. Death usually occurs in less than 1 year. The EEG shows periodic sharp wave complexes. T2-weighted MR images may show hyperintensity in the basal ganglia, and the 14-3-3 protein level is often elevated in the CSF.

Rapidly progressing sporadic CJD may show homozygosity for methionine on codon 129, whereas a more slowly progressing disease often shows homozygosity for valine. Common genetic alterations in familial CJD are D178N and E200K. Mutation of the PrP gene at codon 178 causes aspartic acid (D) to be replaced by asparagine (N), and mutation at codon 200 causes glutamate (E) to be replaced by lysine (K). Insertion mutations have also been identified in familial cases.

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