Alzheimer disease


00:00 / 00:00



Alzheimer disease

Disease-specific Pathology

Cardiovascular Disorders


Aortic valve disease

Atherosclerosis and arteriosclerosis: Pathology review

Atrial septal defect

Cardiac and vascular tumors: Pathology review

Cor pulmonale

Dyslipidemias: Pathology review

Heart failure

Heart failure: Pathology review

Mitral valve disease

Patent ductus arteriosus

Pulmonary embolism

Pulmonary hypertension

Vasculitis: Pathology review

Ventricular septal defect

Endocrine Disorders

Adrenal masses: Pathology review

Multiple endocrine neoplasia: Pathology review

Neuroendocrine tumors of the gastrointestinal system: Pathology review

Pituitary tumors: Pathology review

Thyroid nodules and thyroid cancer: Pathology review

Eye, Ear, Nose, & Throat Disorders

Eye conditions: Inflammation, infections and trauma: Pathology review

Eye conditions: Retinal disorders: Pathology review

Nasal, oral and pharyngeal diseases: Pathology review

Thyroid nodules and thyroid cancer: Pathology review

Vertigo: Pathology review

Gastrointestinal Disorders

Diverticulosis and diverticulitis


Esophageal disorders: Pathology review

Gastrointestinal bleeding: Pathology review


Malabsorption syndromes: Pathology review

Neuroendocrine tumors of the gastrointestinal system: Pathology review

Genetic Disorders

Angelman syndrome

Down syndrome (Trisomy 21)

Edwards syndrome (Trisomy 18)

Ehlers-Danlos syndrome

Fragile X syndrome

Klinefelter syndrome


Marfan syndrome

Myotonic dystrophy


Osteogenesis imperfecta

Patau syndrome (Trisomy 13)

Prader-Willi syndrome

Sickle cell disease (NORD)

Turner syndrome

Hematological Disorders

Blood transfusion reactions and transplant rejection: Pathology review

Metabolic acidosis

Metabolic alkalosis

Non-hemolytic normocytic anemia: Pathology review

Platelet disorders: Pathology review

Respiratory acidosis

Respiratory alkalosis

Thrombosis syndromes (hypercoagulability): Pathology review

Integumentary Disorders

Pigmentation skin disorders: Pathology review

Papulosquamous and inflammatory skin disorders: Pathology review

Vesiculobullous and desquamating skin disorders: Pathology review

Metabolic Disorders


Glucose-6-phosphate dehydrogenase (G6PD) deficiency



Lactose intolerance

Metabolic acidosis

Metabolic alkalosis

Phenylketonuria (NORD)

Tay-Sachs disease (NORD)

Musculoskeletal Disorders

Back pain: Pathology review

Seronegative and septic arthritis: Pathology review

Myalgias and myositis: Pathology review

Neurodevelopmental Disorders

Disruptive, impulse control, and conduct disorders

Fetal alcohol syndrome

Learning disability

Shaken baby syndrome

Tourette syndrome

Neurological Disorders

Alzheimer disease

Headaches: Pathology review

Traumatic brain injury: Pathology review

Spina bifida

Nutritional Disorders


Excess Vitamin A

Excess Vitamin D

Folate (Vitamin B9) deficiency

Iodine deficiency



Niacin (Vitamin B3) deficiency

Vitamin B12 deficiency

Vitamin C deficiency

Vitamin D deficiency

Vitamin K deficiency

Wernicke-Korsakoff syndrome

Zinc deficiency

Psychiatric Disorders


Bipolar disorder

Body dysmorphic disorder

Body focused repetitive disorders

Cluster A personality disorders

Cluster B personality disorders

Cluster C personality disorders

Delusional disorder

Dissociative disorders

Factitious disorder

Major depressive disorder

Neuroleptic malignant syndrome


Premenstrual dysphoric disorder

Schizoaffective disorder

Schizophreniform disorder

Seasonal affective disorder

Serotonin syndrome

Somatic symptom disorder

Renal Disorders




Metabolic acidosis

Metabolic alkalosis

Poststreptococcal glomerulonephritis

Prerenal azotemia

Respiratory Disorders

Chronic bronchitis

Cor pulmonale



Pulmonary embolism

Respiratory acidosis

Respiratory alkalosis

Sexual & Reproductive Disorders

Amenorrhea: Pathology Review

Benign breast conditions: Pathology review

Disorders of sex chromosomes: Pathology review

Erectile dysfunction

Female sexual interest and arousal disorder

Genito-pelvic pain and penetration disorder

Male hypoactive sexual desire disorder

Orgasmic dysfunction

Penile conditions: Pathology review

Testicular and scrotal conditions: Pathology review

Uterine disorders: Pathology review

Vaginal and vulvar disorders: Pathology review

Sleep Disorders



Narcolepsy (NORD)

Night terrors


Alzheimer disease


0 / 18 complete

USMLE® Step 1 questions

0 / 5 complete

High Yield Notes

9 pages


Alzheimer disease

of complete


USMLE® Step 1 style questions USMLE

of complete

A pathologist is examining brain biopsies from a patient who died from a neurodegenerative condition following an episode of aspiration pneumonia. A tissue sample from the patient is demonstrated below:

Image reproduced from Wikimedia Commons

Further staining reveals patchy red plaques that become yellow when viewed under polarized light. Which of the following clinical courses was most likely seen in this patient? 

External References

First Aid








Acetylcholinesterase (AChE) inhibitors

Alzheimer disease p. 569

Alzheimer disease p. 538

amalyoidosis in p. 216

Down syndome and p. 61

drug therapy for p. 241, 569

labs/findings p. 722, 731

neurotransmitters for p. 512

ventriculomegaly with p. 540

Early-onset Alzheimer disease p. 61

Galantamine p. 241

for Alzheimer disease p. 569


Alzheimer disease drugs p. 569

Rivastigmine p. 241

Alzheimer disease p. 569


Content Reviewers

Rishi Desai, MD, MPH


Tanner Marshall, MS

Dementia isn’t technically a disease, but more of a way to describe a set of symptoms like poor memory and difficulty learning new information, which can make it really hard to function independently.

Usually dementia’s caused by some sort of damage to the cells in the brain, which can be caused by a variety of diseases. Alzheimer’s disease, now referred to as Alzheimer disease, is the most common cause of dementia.

Alzheimer disease is considered a neurodegenerative disease, meaning it causes the degeneration, or loss, of neurons in the brain, particularly in the cortex. This, as you might expect, leads to the symptoms characteristic of dementia.

Although the cause of Alzheimer disease isn’t completely understood, two major players that are often cited in its progression are plaques and tangles.

Alright, so here we’ve got the cell membrane of a neuron in the brain. In the membrane, you’ve got this molecule called amyloid precursor protein, or APP, one end of this guy’s in the cell, and the other end’s outside the cell. It’s thought that this guy helps the neuron grow and repair itself after an injury.

Since APP’s a protein, just like other proteins, it gets used and over time it gets broken down and recycled.

Normally, it gets chopped up by an enzyme called alpha secretase and it’s buddy, gamma secretase.

This chopped up peptide is soluble and goes away, and everything’s all good.

If another enzyme, beta secretase, teams up with gamma secretase instead, then we’ve got a problem, and this leftover fragment isn’t soluble, and creates a monomer called amyloid beta.

These monomers tend to be chemically “sticky”, and bond together just outside the neurons, and form what are called beta-amyloid plaques—these clumps of lots of these monomers.

These plaques can potentially get between the neurons, which can get in the way of neuron-to-neuron signaling.

If the brain cells can’t signal and relay information, then brain functions like memory can be seriously impaired.

It’s also thought that these plaques can start up an immune response and cause inflammation which might damage surrounding neurons.

Amyloid plaque can also deposit around blood vessels in the brain, called amyloid angiopathy, which weakens the walls of the blood vessels and increases the risk of hemorrhage, or rupture and blood loss.

Here’s an image of amyloid plaque on histology, these clumps are buildups of beta amyloid, and this is happening outside the cell.


  1. "Robbins Basic Pathology" Elsevier (2017)
  2. "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
  3. "Pathophysiology of Disease: An Introduction to Clinical Medicine 8E" McGraw-Hill Education / Medical (2018)
  4. "Alzheimer's disease" BMJ (2009)
  5. "Early-onset Alzheimer's Disease: Nonamnestic Subtypes and Type 2 AD" Archives of Medical Research (2012)
  6. "Pathogenic tau-induced piRNA depletion promotes neuronal death through transposable element dysregulation in neurodegenerative tauopathies" Nature Neuroscience (2018)

Copyright © 2023 Elsevier, except certain content provided by third parties

Cookies are used by this site.

USMLE® is a joint program of the Federation of State Medical Boards (FSMB) and the National Board of Medical Examiners (NBME). COMLEX-USA® is a registered trademark of The National Board of Osteopathic Medical Examiners, Inc. NCLEX-RN® is a registered trademark of the National Council of State Boards of Nursing, Inc. Test names and other trademarks are the property of the respective trademark holders. None of the trademark holders are endorsed by nor affiliated with Osmosis or this website.