This woman most likely suffered from Creutzfeldt-Jakob Disease (CJD), which results from the conversion of an a-helix in a normal protein, termed prion protein (PrPc), to a ß-pleated form. The new ß-pleated protein (PrPSc) resists degradation and facilitates conversion of normal proteins to the abnormal form.
The accumulation of abnormal ß-pleated prion protein (PrPSc) results in "spongiform encephalopathy," characterized by rapidly progressive mental deterioration (often with behavioral abnormalities). It is distinguished from other causes of dementia by its rapidly progressive course (patients usually die within one year of symptom onset), prominent myoclonus (especially provoked by startle), and prominent gait disturbance.
Santacruz and Swagerty discuss how CJD should be on the differential for etiologies of dementia.
Sikorska B et al. point out in their review of the disease that there are four types of Creutzfeldt-Jakob Disease known: 1. Sporadic (sCJD), 2. familial or genetic (gCJD), 3. iatrogenic (iCJD), and 4. variant CJD.
Head and Ironside note that the main histologic features are spongiform change, neuronal loss without inflammation, and accumulation of the abnormal prion protein.
Image A shows Creutzfeldt-Jakob Disease pathology on low power.
Image B shows Creutzfeldt-Jakob Disease pathology on high power.
Image C shows the normal prion protein (PrPc) and the abnormal prion protein (PrPSC).
Answer 1: Describes Parkinson disease which generally progresses more slowly. Characteristic presentation is pill-rolling tremor, cogwheel rigidity, akinesia, and postural instability.
Answer 2: Describes a central demyelinating disease, such as multiple sclerosis, which is characterized by scanning speech, intention tremor, incontinence, internuclear ophthalmoplegia, and nystagmus.
Answer 3: Describes a peripheral demyelinating disease, such as Guillain-Barré syndrome, which presents with symmetric ascending muscle weakness in the distal lower extremities.
Answer 5: Describes Pick disease, which also presents with dementia and personality changes, but is chronic rather than subacute in progression (patients almost never die within 12 months of onset). Also, myoclonus with startle is not typical.
Sikorska B, Knight R, Ironside JW, Liberski PP. Creutzfeldt-Jakob disease. Adv Exp Med Biol. 2012;724:76-90. doi: 10.1007/978-1-4614-0653-2_6.
PMID:22411235 (Link to Abstract)
Head MW, Ironside JW. Review: Creutzfeldt-Jakob disease: prion protein type, disease phenotype and agent strain. Neuropathol Appl Neurobiol. 2012 Jun;38(4):296-310. doi: 10.1111/j.1365-2990.2012.01265.x.
PMID:22394291 (Link to Abstract)
Santacruz KS, Swagerty D. Early diagnosis of dementia. Am Fam Physician. 2001 Feb 15;63(4):703-13, 717-8. Review. PubMed PMID: 11237085
PMID:11237085 (Link to Abstract)
USMLE World Step 1 QBank Question #912. Copyright © USMLEWorld, LLC 2012