Alzheimer's disease

AlzheimerAlzheimer’s diseaseAlzheimer diseaseAlzheimersAlzheimer’sAlzheimer's dementiaAlzheimer's disease (AD)Alzheimers diseaselate-onset Alzheimer's diseaseAD
Alzheimer's disease (AD), also referred to simply as Alzheimer's, is a chronic neurodegenerative disease that usually starts slowly and gradually worsens over time.wikipedia
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Dementia

senilesenilitysenile dementia
It is the cause of 60–70% of cases of dementia.
The most common type of dementia is Alzheimer's disease, which makes up 50% to 70% of cases.

Head injury

head traumahead injurieshead
Other risk factors include a history of head injuries, depression, and hypertension.
Alzheimer’s disease, for example, is much more likely to develop in a person who has experienced a head injury.

Neurofibrillary tangle

neurofibrillary tanglestanglestangle diseases
The disease process is associated with plaques and neurofibrillary tangles in the brain.
Neurofibrillary tangles (NFTs) are aggregates of hyperphosphorylated tau protein that are most commonly known as a primary marker of Alzheimer's disease.

Primary progressive aphasia

progressive aphasiaaphasiaprimary progressive aphasia (PPA)
As the disease advances, symptoms can include problems with language, disorientation (including easily getting lost), mood swings, loss of motivation, not managing self-care, and behavioural issues.
Primary progressive aphasias have a clinical and pathological overlap with the frontotemporal lobar degeneration (FTLD) spectrum of disorders and Alzheimer's disease.

Alois Alzheimer

Alios AlzheimerDr. Alois Alzheimer
It was first described by, and later named after, German psychiatrist and pathologist Alois Alzheimer in 1906.
Alzheimer is credited with identifying the first published case of "presenile dementia", which Kraepelin would later identify as Alzheimer's disease.

Anomic aphasia

anomiaamnesic aphasiadysnomia
Speech difficulties become evident due to an inability to recall vocabulary, which leads to frequent incorrect word substitutions (paraphasias).
Patients with Alzheimer's disease have speech problems linked to dementia or progressive aphasias, which can include anomia.

Ageing

agingageoctogenarian
The first symptoms are often mistakenly attributed to ageing or stress.
The spectrum ranges from mild cognitive impairment to the neurodegenerative diseases of Alzheimer's disease, cerebrovascular disease, Parkinson's disease and Lou Gehrig's disease.

Mild cognitive impairment

mild cognitive impairment (MCI)MCImild cognitive impairment (MCI)
The preclinical stage of the disease has also been termed mild cognitive impairment (MCI).
Although MCI can present with a variety of symptoms, when memory loss is the predominant symptom it is termed "amnestic MCI" and is frequently seen as a prodromal stage of Alzheimer's disease.

Early-onset Alzheimer's disease

early-onset Alzheimerfamilial Alzheimer's diseaseearly onset Alzheimer's disease
It most often begins in people over 65 years of age, although 4–5% of cases are early-onset Alzheimer's.
Early-onset Alzheimer's disease, also called early-onset Alzheimer's, or early-onset AD, is Alzheimer's disease diagnosed before the age of 65.

Psychosis

psychoticpsychosespsychotic break
Behavioural problems or psychosis due to dementia are often treated with antipsychotics, but this is not usually recommended, as there is little benefit with an increased risk of early death.
The volume of the hippocampus and parahippocampus is related to paranoid delusions in Alzheimer's disease, and has been reported to be abnormal post mortem in one person with delusions.

Wandering (dementia)

wandering
Common manifestations are wandering, irritability and labile affect, leading to crying, outbursts of unpremeditated aggression, or resistance to caregiving.
Although it occurs in several types of dementia, wandering is especially common in people with Alzheimer's disease (AD).

Pseudobulbar affect

emotional labilityemotionalismLabile affect
Common manifestations are wandering, irritability and labile affect, leading to crying, outbursts of unpremeditated aggression, or resistance to caregiving.
Where patients have significant cognitive deficits (e.g., Alzheimer's) it can be unclear whether it is true PBA as opposed to a grosser form of emotional dysregulation, but patients with intact cognition often report the symptom as disturbing.

Presenilin

presenilin-1presenilinspresenilins 1 and 2
Most of autosomal dominant familial AD can be attributed to mutations in one of three genes: those encoding amyloid precursor protein (APP) and presenilins 1 and 2.
They were first identified in screens for mutations causing early onset forms of familial Alzheimer's disease by Peter St George-Hyslop at the Centre for Research in Neurodegenerative Diseases at the University of Toronto, and now also at the University of Cambridge.

Amyloid precursor protein

APP(APPamyloid beta (A4) precursor protein
Most of autosomal dominant familial AD can be attributed to mutations in one of three genes: those encoding amyloid precursor protein (APP) and presenilins 1 and 2. Support for this postulate comes from the location of the gene for the amyloid precursor protein (APP) on chromosome 21, together with the fact that people with trisomy 21 (Down Syndrome) who have an extra gene copy almost universally exhibit at least the earliest symptoms of AD by 40 years of age.
APP is best known as the precursor molecule whose proteolysis generates beta amyloid (Aβ), a polypeptide containing 37 to 49 amino acid residues, whose amyloid fibrillar form is the primary component of amyloid plaques found in the brains of Alzheimer's disease patients.

Mood swing

mood changesaltered moodmood
As the disease advances, symptoms can include problems with language, disorientation (including easily getting lost), mood swings, loss of motivation, not managing self-care, and behavioural issues.
Degenerative diseases of the human central nervous system such as Parkinson's disease, Alzheimer's disease, multiple sclerosis, and Huntington's disease may also produce mood swings.

Apolipoprotein E

APOEAPOE4APOE ε4
The best known genetic risk factor is the inheritance of the ε4 allele of the apolipoprotein E (APOE).
It is implicated in Alzheimer's disease and cardiovascular disease.

Single-nucleotide polymorphism

single nucleotide polymorphismSNPSNPs
Many SNPs are associated with Alzheimer's with a 2018 study adding 30 SNPs by differentiating AD into 6 categories, including memory, language, visuospatial, and executive functioning.
For example, a single-base mutation in the APOE (apolipoprotein E) gene is associated with a lower risk for Alzheimer's disease.

Neurodegeneration

neurodegenerativeneurodegenerative diseaseneurodegenerative diseases
Alzheimer's disease (AD), also referred to simply as Alzheimer's, is a chronic neurodegenerative disease that usually starts slowly and gradually worsens over time.
Many neurodegenerative diseases – including amyotrophic lateral sclerosis, Parkinson's disease, Alzheimer's disease, and Huntington's disease – occur as a result of neurodegenerative processes.

Aging brain

Ageing braincognitive agingaging
DR6 is highly expressed in the human brain regions most affected by Alzheimer's, so it is possible that the N-APP/DR6 pathway might be hijacked in the ageing brain to cause damage.
Aging is a major risk factor for most common neurodegenerative diseases, including mild cognitive impairment, dementias including Alzheimer's disease, cerebrovascular disease, Parkinson's disease and Lou Gehrig's disease.

Sundowning

Sundown syndromeSundowning (dementia)
Sundowning can also appear.
Most commonly associated with Alzheimer's disease, but also found in those with other forms of dementia, the term "sundowning" was coined due to the timing of the patient's confusion.

Major depressive disorder

depressionclinical depressionmajor depression
Other risk factors include a history of head injuries, depression, and hypertension.
Subjective cognitive complaints appear in older depressed people, but they can also be indicative of the onset of a dementing disorder, such as Alzheimer's disease.

Amyloid beta

beta amyloidbeta-amyloidβ-amyloid
Most mutations in the APP and presenilin genes increase the production of a small protein called Aβ42, which is the main component of senile plaques.
Amyloid beta (Aβ or Abeta) denotes peptides of 36–43 amino acids that are crucially involved in Alzheimer's disease as the main component of the amyloid plaques found in the brains of people with Alzheimer's disease.

Apraxia

apraxiasdressing apraxiaPraxis
In a small percentage, difficulties with language, executive functions, perception (agnosia), or execution of movements (apraxia) are more prominent than memory problems.
Lesions may be due to stroke, acquired brain injuries, or neurodegenerative diseases such as Alzheimer's disease or other dementias, Parkinson's disease, or Huntington's disease.

Down syndrome

Down's syndrometrisomy 21Downs Syndrome
Support for this postulate comes from the location of the gene for the amyloid precursor protein (APP) on chromosome 21, together with the fact that people with trisomy 21 (Down Syndrome) who have an extra gene copy almost universally exhibit at least the earliest symptoms of AD by 40 years of age.
Many (15%) who live 40 years or longer develop Alzheimer’s disease.

Complement receptor 1

CR1CD35Complement component receptor 1
More recent genome-wide association studies (GWAS) have found 19 areas in genes that appear to affect the risk. These genes include: CASS4, CELF1, FERMT2, HLA-DRB5, INPP5D, MEF2C, NME8, PTK2B, SORL1, ZCWPW1, SlC24A4, CLU, PICALM, CR1, BIN1, MS4A, ABCA7, EPHA1, and CD2AP.
Certain alleles of this gene have been statistically associated with an increased risk of developing late-onset Alzheimer's disease.