Thalamic form of Creutzfeldt-Jakob disease or fatal insomnia? Report of a sporadic case with normal prion protein genotype.

We describe a 68-year-old man with a 53-month history of progressive dementia and clinical features of a progressive supranuclear palsy-like syndrome and dysautonomia. In the late stage of his illness, the patient also developed generalized myoclonic seizures. There was no family history of similar disorders. Histological examination revealed neuronal loss and gliosis with spongiosis in the cerebral cortex. In addition, more severe neuronal loss and gliosis without spongiosis were observed in the thalamus, especially in the anterior ventral and mediodorsal nuclei, and the inferior olivary nucleus. There was also obvious loss of Purkinje cells. Immunohistochemically, no protease-resistant prion protein (PrPres)-positive structures were demonstrated. However, Western blotting revealed the presence of PrPres in the cerebral cortex. This patient had a wild type of PrP genotype. We initially considered this to be a case of the thalamic form of Creutzfeldt-Jakob disease (CJD) with a long duration. However, it is noteworthy that essentially similar pathology, albeit with less severe cerebral cortical changes, has also been reported in fatal familial insomnia, a newly identified phenotypically different prion disease with a mutation in the PrP gene. On the basis of clinicopathological features, we eventually felt that this patient was more likely to have been a sporadic case of fatal insomnia (FI) of long duration. The present case appears to draw further attention to the possible relationship between CJD and FI.