Pathophysiology
1) degenerative disease of CNS caused by presence of infectious protein called a prion 2) presents with myoclonus and dementia; relentlessly progresses to death, usually within 1 year 3) in the past decade new-variant CJD has been described that is a human infection by the etiologic agent causing bovine spongiform encephalopathy (“mad cow” disease)
Signs and Symptoms
1) in one third of cases a prodrome of malaise, fatigue, sleep problems, headache, and weight loss occurs 2) myoclonus 3) dementia 4) choreoathetoid movements 5) vision deficits
Characteristic Test Findings
EEG – 1) early in disease can be normal or show only scattered theta activity 2) as disease progresses episodic triphasic and polyphasic spikes are seen
Histology/Gross Pathology
1) affected areas of brain – cerebral cortex, thalamus, putamen, caudate nucleus, and cerebellar cortex, which show spongiform degeneration 2) 10% of patients show amyloid plaques (“florid plaques” in new-variant CJD)
Associated Conditions
transmission known to occur from – 1) corneal transplants 2) infected EEG leads 3) neurosurgical procedures 4) dura matter grafts 5) human growth hormone 6) pituitary gonadotropin therapy
Biochemistry
prions lack nucleic acid (no DNA or RNA) 2) abnormal prions reproduce by binding to the normal form of the protein, causing it to change its form from high in alpha helix, low in beta sheet to vice versa
Inheritance/Epidemiology
1) prion disease exists in familial, sporadic, and infectious forms 2) gene for the prion protein occurs on the short arm of chromosome 20 3) most common age group of sporadic CJD is 50-75 years; new variant CJD occurs in areas of mad cow disease and affects mostly teenagers and young adults.
Treatment
There is no effective treatment, but several drugs are being tested on laboratory animals
Tips for USMLE
1) if question mentions alpha to beta transformation of proteins, think CJD 2) if there is fever, increased sed rate, leukocytosis, or a significant change in CSF, it is not CJD 3) best way to diagnose CJD is brain biopsy with spongiform degeneration 4) best way to diagnose CJD clinically – presence of myoclonus, dementia, and electrical spikes on EEG (other diseases that have myoclonus and dementia are Alzheimer’s disease, cryptococcal encephalitis, and Unverricht-Lundborg disease)
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