Answer
Prion diseases, also known as transmissible spongiform encephalopathies, are a family of rapidly progressive neurodegenerative diseases. [9] These diseases are unique in two ways. First, they are transmissible but not infectious. Second, the transmitting agent is a misfolded protein called the prion protein, capable of causing native, normally folded protein to adopt this disease-associated conformation when introduced into an organism. [9] Spontaneous misfolding of the prion protein is the most common cause.
The transmissibility of prion diseases was first described in studying an endemic prion disease called kuru among the Fore tribe of Papua New Guinea. [9] Kuru is characterized by rapid loss of motor and intellectual function, body tremors, and pathologic laughter. Further study revealed that Fore funeral practice included cannibalism. Ever since this practice was outlawed among the Fore, the disease has disappeared.
Creutzfeldt-Jakob disease (CJD) is the most common form of prion disease and occurs at a rate of approximately one case per one million population per year. Both sporadic and autosomal-dominant genetic forms of CJD exist. [9] Pathologically, prion diseases are characterized by spongiform encephalopathy and deposition of highly protease-resistant prion protein aggregates (see the image below). Spongiform encephalopathy—the appearance of coalescent vacuoles within the grey matter neuropil—is accompanied by neuron loss and gliosis. The vacuoles are dilated neuronal processes. Diagnosis of prion diseases requires biochemical analyses of the glycosylated forms of the abnormal prion protein.
If a prion disease is suspected by a physician, contacting the National Prion Disease Pathology Surveillance Center is imperative.
Dementia pathology. A: Hematoxylin and eosin staining at 400× magnification of the cerebral cortex reveals the coalescent clear vesicles characteristic of spongiform encephalopathy. B: Immunohistochemical staining (brown) against protease-resistant prion protein reveals the granular immunoreactivity seen in Creutzfeldt-Jakob disease.
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Dementia pathology. Bielschowsky silver staining of the cortex at 400× magnification demonstrates a neurofibrillary tangle (black arrow) and a neuritic plaque (white arrow).
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Dementia pathology. Congo red staining of a small cortical artery at 400× magnification demonstrates salmon-colored amyloid deposition in the media of the vessel.
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Dementia pathology. A: Hematoxylin-eosin-Luxol fast blue staining of the basal ganglia at 100× magnification demonstrates a cavitary infarct. Calcific medial sclerosis of small arteries is also present. B: At 400× magnification, numerous foamy macrophages are present within the center of the infarcted tissue.
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Dementia pathology. A: Hematoxylin and eosin staining of the substantia nigra at 400× magnification demonstrates multiple Lewy bodies within a pigmented neuron. The Lewy bodies are round with a densely eosinophilic core surrounded by a clear halo. B: Immunohistochemical staining (brown) against alpha-synuclein at 400× magnification reveals a round Lewy body within the soma of a neuron.
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Dementia pathology. Comorbid brain pathologies are common in the elderly population. This Venn diagram demonstrates the co-occurrence of brain pathologies as evident from population-based autopsy studies of brain aging.
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Dementia pathology. A: Hematoxylin and eosin staining at 400× magnification of the dentate fascia of the hippocampus reveals round eosinophilic Pick bodies (arrows) in the soma of granular neurons. B: Immunohistochemical staining (brown) against tau at 400× magnification reveals round intraneuronal Pick bodies in cortical neurons.
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Dementia pathology. A: Hematoxylin and eosin staining at 400× magnification of the cerebral cortex reveals the coalescent clear vesicles characteristic of spongiform encephalopathy. B: Immunohistochemical staining (brown) against protease-resistant prion protein reveals the granular immunoreactivity seen in Creutzfeldt-Jakob disease.
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Dementia pathology. Immunohistochemical staining (brown) against tau at 400× magnification reveals glial immunoreactivity that is characteristic of this case of cortico-basal ganglionic degeneration.
