questions 4

Alzheimer Disease

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Topic updated on 08/28/17 10:34pm

Snapshot
  • A 78-year-old man presents to his primary care clinic and is accompanied by his wife. He feels well, but his wife is concerned that he has become more confused over the past few weeks. He enjoys socializing with family and friends, but sometimes has difficulty finding words and recently forgot his niece's name. He walks around his neighborhood for exercise, but has the tendency to wander and get lost. He has a history of hypertension and atrial fibrillation. Current medications are warfarin and dronedarone. Physical exam is unremarkable. Recent lab results were within normal limits. 
Introduction
  • Most common cause of dementia in the elderly
  • Pathogenesis remains unclear, but involves
    • accumulation of neurotoxic proteins, amyloid beta (Aβ-amyloid) and tau
    • ↓ ACh neurotransmission by cholinergic neurons in the nucleus basalis of Meynert 
Causes
  • Majority are sporadic
  • Genetic forms
    • early-onset
      • rare
      • autosomal dominant
      • can involve presenilin mutations 
        • presenilin-1 (chromosome 14)
        • presenilin-2 (chromosome 1)
      • associated with Down syndrome (trisomy 21)
        • ↑ risk of developing Alzheimer's because APP gene is located on chromosome 21  
        • commonly presents before age 40 
    • late-onset 
      • allele variations of apolipoprotein E (APOE) on chromosome 19 affect risk of developing Alzheimer's disease 
        • ε4 is associated with increased risk
        • ε2 is associated with decreased risk
Presentation
  • Progressive symptoms
    • mild
      • short-term memory loss
    • moderate 
      • inability to learn/recall information
      • long-term memory loss
      • wandering
      • mood swings and personality changes including aggression
    • severe
      • incontinence
      • gait disturbance
      • unable to perform ADLs
Evaluation
  • Clinical diagnosis of exclusion
    • confirmation is autopsy histology
  • Characteristic findings on histopathology (see above image):
    • senile/neuritic plaques
      • extracellular Aβ-amyloid core derived from amyloid precursor protein (APP) 
        • APP normally degraded via α-cleavage
        • β-cleavage of APP results in Aβ-amyloid
    • neurofibrillary tangles
      • intracellular aggregations of hyperphosphorylated tau protein
        • tau is an insoluble cytoskeletal element (microtubule-associated protein)
      • tangles correlate with degree of dementia
    • neuronal degeneration
      • results in diffuse cortical atrophy
      • widening of sulci, narrowing of gyri, expansion of the ventricles
Treatment
  • See Alzheimer's drugs
Prognosis, Prevention, and Complications
  • Complications
    • amyloidosis may result in angiopathy
    • results in weakened vessel walls and can lead to rupture with intracranial hemorrhage
  • Most common cause of death is infection
    • mental status changes associated with sepsis are not detected when superimposed on baseline Alzheimer's disease


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Qbank (2 Questions)

TAG
(M1.NE.72) A 38-year-old man with mental retardation (IQ 50), facial features that include epicanthic folds and low-set small ears, and hands pictured in Figure A, is brought in by his elderly parents, who provide constant care. They are concerned that over the past 3 years, he has become increasingly forgetful and less interested in conversing and sharing his thoughts. If a post-mortem brain autopsy were conducted, the most likely histopathological feature in his brain underlying these changes would be: Topic Review Topic
FIGURES: A          

1. Beta-amyloid plaques and neurofibrillary tangles of phosphorylated tau
2. Clumps of alpha-synuclein and ubiquitin protein in neurons
3. Multiple, scattered ischemic lesions in the cortex
4. Marked loss of cells in the head of caudate with dilated lateral ventricles
5. Many round vacuoles in the gray matter consistent with spongiform changes

PREFERRED RESPONSE ▶
TAG
(M1.NE.74) A 40-year-old male with Down syndrome is brought to your clinic by his mother. She reports that over the past few months he has started having difficulty managing his daily routine at his assisted-living facility and no longer seems like himself. She says that last week he wandered away from the facility and was brought back by police. Additionally, he has stopped taking his regular antiepileptic medication, and she is concerned that he might have a seizure. TSH is checked and is normal. Which of the following is most likely to be responsible for this man's current presentation? Topic Review Topic

1. Expansion of trinucleotide repeats
2. Abnormal protein metabolism
3. Hormone deficiency
4. Premature degradation of a protein
5. Nutritional deficiency

PREFERRED RESPONSE ▶
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