Wiktionary
n. (context pathology English) Any of a class of neurodegenerative diseases associated with the pathological aggregation of tau protein
Wikipedia
Not to be confused with Tautopathy, an alternative medicine practice without scientific merit or credibility.
Tauopathies are a class of neurodegenerative diseases associated with the pathological aggregation of tau protein in neurofibrillary or gliofibrillary tangles in the human brain. Tangles are formed by hyperphosphorylation of a microtubule-associated protein known as tau, causing it to aggregate in an insoluble form. (These aggregations of hyperphosphorylated tau protein are also referred to as paired helical filaments). The precise mechanism of tangle formation is not completely understood, and it is still controversial as to whether tangles are a primary causative factor in the disease or play a more peripheral role. Primary tauopathies, i.e., conditions in which neurofibrillary tangles are predominantly observed, include:
- Primary age-related tauopathy (PART)/Neurofibrillary tangle-predominant senile dementia, with NFTs similar to AD, but without plaques.
- Dementia pugilistica ( chronic traumatic encephalopathy)
- Progressive supranuclear palsy
- Corticobasal degeneration
- Chronic traumatic encephalopathy
- Frontotemporal dementia and parkinsonism linked to chromosome 17
- Lytico-Bodig disease (Parkinson-dementia complex of Guam)
- Ganglioglioma and gangliocytoma
- Meningioangiomatosis
- Postencephalitic parkinsonism
- Subacute sclerosing panencephalitis
- As well as lead encephalopathy, tuberous sclerosis, Hallervorden-Spatz disease, and lipofuscinosis
Neurofibrillary tangles were first described by Alois Alzheimer in one of his patients suffering from Alzheimer's disease (AD), which is considered a secondary tauopathy. AD is also classified as an amyloidosis because of the presence of senile plaques.
The degree of NFT involvement in AD is defined by Braak stages. Braak stages I and II are used when NFT involvement is confined mainly to the transentorhinal region of the brain, stages III and IV when there's also involvement of limbic regions such as the hippocampus, and V and VI when there's extensive neocortical involvement. This should not be confused with the degree of senile plaque involvement, which progresses differently.
In Pick's disease and corticobasal degeneration tau proteins are deposited in the form of inclusion bodies within swollen or "ballooned" neurons.
Argyrophilic grain disease (AGD), another type of dementia, is marked by the presence of abundant argyrophilic grains and coiled bodies on microscopic examination of brain tissue. Some consider it to be a type of Alzheimer disease. It may co-exist with other tauopathies such as progressive supranuclear palsy and corticobasal degeneration, and also Pick's disease.
Huntington's disease: a neurodegenerative disease caused by a CAG tripled expansion in huntingtin gene is the most recently described tauopathy (Fernandez-Nogales et al. Nat Med 2014). JJ Lucas and co-workers demonstrated that in HD brains tau levels are increased and that the 4R/3R balance is altered. In addition, in this study, JJ Lucas shows intranuclear insoluble deposits of tau. These "Lucas rods" were also found in Alzheimer's disease brains.
Tauopathies often have overlap with synucleinopathies, possibly because of interaction between the synuclein and tau proteins.
The non-Alzheimer's tauopathies are sometimes grouped together as "Pick's complex" because of their association with Frontotemporal dementia, or Frontotemporal lobar degeneration.