Primary Age-Related Tauopathy (PART)

Overview

Primary age-related tauopathy (PART) is a neuropathologic entity defined by Alzheimer-type neurofibrillary tau pathology in medial temporal structures with absent or minimal amyloid-beta deposition.^{1Primary age-related tauopathy (PART): a common pathology associated with human aging2014 · Acta Neuropathologica · PMID 25348064Open reference2Consensus criteria for the neuropathologic diagnosis of primary age-related tauopathy (PART)2022 · Acta Neuropathologica · PMID 35503043Open reference} PART is common in aging brains and is frequently identified in autopsy cohorts of older adults, including individuals without dementia.^{1Primary age-related tauopathy (PART): a common pathology associated with human aging2014 · Acta Neuropathologica · PMID 25348064Open reference3Defining and phenotyping age-related tauopathy in the context of cognitive decline2019 · Acta Neuropathologica · PMID 30874984Open reference} The consensus framework positions PART as a tau-predominant age-related process that can contribute to cognitive impairment but is biologically distinct from typical Alzheimer disease when amyloid burden remains low.^{2Consensus criteria for the neuropathologic diagnosis of primary age-related tauopathy (PART)2022 · Acta Neuropathologica · PMID 35503043Open reference4Primary age-related tauopathy versus Alzheimer disease: similarities and differences2015 · Acta Neuropathologica · PMID 26486986Open reference}

Core Diagnostic Concept

Consensus criteria define PART by combining tau stage (Braak NFT stage) and amyloid phase (Thal phase):^{2Consensus criteria for the neuropathologic diagnosis of primary age-related tauopathy (PART)2022 · Acta Neuropathologica · PMID 35503043Open reference}

• Definite PART: Braak stage I-IV tau pathology with Thal amyloid phase 0

• Possible PART: Braak stage I-IV tau pathology with limited amyloid deposition (low Thal phase)

• Cases with substantial amyloid deposition are generally classified within the Alzheimer disease neuropathologic continuum rather than PART

This classification resolves older terminology such as “tangle-predominant senile dementia” and aligns clinicopathologic studies under a single standard.^{1Primary age-related tauopathy (PART): a common pathology associated with human aging2014 · Acta Neuropathologica · PMID 25348064Open reference2Consensus criteria for the neuropathologic diagnosis of primary age-related tauopathy (PART)2022 · Acta Neuropathologica · PMID 35503043Open reference}

Neuropathology

PART pathology centers on transentorhinal/entorhinal and hippocampal regions and may extend into limbic cortex with increasing Braak stage.^{1Primary age-related tauopathy (PART): a common pathology associated with human aging2014 · Acta Neuropathologica · PMID 25348064Open reference2Consensus criteria for the neuropathologic diagnosis of primary age-related tauopathy (PART)2022 · Acta Neuropathologica · PMID 35503043Open reference}0 Tau biochemistry overlaps with Alzheimer-type paired helical filament tau, but the burden and network spread are usually more restricted than in advanced Alzheimer disease.^{2Consensus criteria for the neuropathologic diagnosis of primary age-related tauopathy (PART)2022 · Acta Neuropathologica · PMID 35503043Open reference}1^{2Consensus criteria for the neuropathologic diagnosis of primary age-related tauopathy (PART)2022 · Acta Neuropathologica · PMID 35503043Open reference}2

Common findings include:^{2Consensus criteria for the neuropathologic diagnosis of primary age-related tauopathy (PART)2022 · Acta Neuropathologica · PMID 35503043Open reference}3^{2Consensus criteria for the neuropathologic diagnosis of primary age-related tauopathy (PART)2022 · Acta Neuropathologica · PMID 35503043Open reference}4

• Neurofibrillary tangles and neuropil threads in medial temporal lobe

• Relative sparing of neocortical amyloid plaque pathology

• Frequent co-pathology in late life (e.g., cerebrovascular disease, Lewy pathology, LATE-NC)

Epidemiology and Clinical Phenotype

Autopsy data indicate that PART is prevalent in advanced age and often coexists with other proteinopathies, complicating clinicopathologic attribution of symptoms.^{2Consensus criteria for the neuropathologic diagnosis of primary age-related tauopathy (PART)2022 · Acta Neuropathologica · PMID 35503043Open reference}5^{2Consensus criteria for the neuropathologic diagnosis of primary age-related tauopathy (PART)2022 · Acta Neuropathologica · PMID 35503043Open reference}6 Many individuals with low-stage PART remain cognitively intact, while higher tau burden and co-pathology increase risk of measurable impairment.^{2Consensus criteria for the neuropathologic diagnosis of primary age-related tauopathy (PART)2022 · Acta Neuropathologica · PMID 35503043Open reference}7^{2Consensus criteria for the neuropathologic diagnosis of primary age-related tauopathy (PART)2022 · Acta Neuropathologica · PMID 35503043Open reference}8^{2Consensus criteria for the neuropathologic diagnosis of primary age-related tauopathy (PART)2022 · Acta Neuropathologica · PMID 35503043Open reference}9

Typical clinical profile when symptomatic:^{1Primary age-related tauopathy (PART): a common pathology associated with human aging2014 · Acta Neuropathologica · PMID 25348064Open reference}0^{1Primary age-related tauopathy (PART): a common pathology associated with human aging2014 · Acta Neuropathologica · PMID 25348064Open reference}1

• Mild episodic memory and executive dysfunction

• Slower progression than biomarker-confirmed Alzheimer disease in many cohorts

• Heterogeneous phenotype driven by co-pathology burden

Biomarkers and Differential Diagnosis

In vivo diagnosis remains challenging because currently deployed AD biomarkers are optimized for amyloid-positive Alzheimer biology.^{1Primary age-related tauopathy (PART): a common pathology associated with human aging2014 · Acta Neuropathologica · PMID 25348064Open reference}2 PART-like cases often appear in A-/T+ or SNAP-like biomarker patterns depending on assay platform and stage.^{1Primary age-related tauopathy (PART): a common pathology associated with human aging2014 · Acta Neuropathologica · PMID 25348064Open reference}3^{1Primary age-related tauopathy (PART): a common pathology associated with human aging2014 · Acta Neuropathologica · PMID 25348064Open reference}4

Differential diagnosis should prioritize:^{1Primary age-related tauopathy (PART): a common pathology associated with human aging2014 · Acta Neuropathologica · PMID 25348064Open reference}5^{1Primary age-related tauopathy (PART): a common pathology associated with human aging2014 · Acta Neuropathologica · PMID 25348064Open reference}6

• Alzheimer disease neuropathologic change (A+T+ profiles)

• Limbic-predominant age-related TDP-43 encephalopathy (LATE)

• Argyrophilic grain disease and other limbic tauopathies

• Mixed vascular-neurodegenerative cognitive syndromes

Genetics and Risk Modifiers

Unlike late-onset Alzheimer disease, PART does not show a strong, consistent APOE e4 enrichment across all cohorts; genetic architecture appears more heterogeneous and likely influenced by age-related resilience/vulnerability factors.^{1Primary age-related tauopathy (PART): a common pathology associated with human aging2014 · Acta Neuropathologica · PMID 25348064Open reference}7^{1Primary age-related tauopathy (PART): a common pathology associated with human aging2014 · Acta Neuropathologica · PMID 25348064Open reference}8 MAPT background may modulate tau burden, but definitive Mendelian PART genetics are not established.^{1Primary age-related tauopathy (PART): a common pathology associated with human aging2014 · Acta Neuropathologica · PMID 25348064Open reference}9^{3Defining and phenotyping age-related tauopathy in the context of cognitive decline2019 · Acta Neuropathologica · PMID 30874984Open reference}0

Clinical and Research Implications

Standardized PART classification has practical implications for clinical trial interpretation and precision phenotyping in geriatric neurology:^{3Defining and phenotyping age-related tauopathy in the context of cognitive decline2019 · Acta Neuropathologica · PMID 30874984Open reference}1^{3Defining and phenotyping age-related tauopathy in the context of cognitive decline2019 · Acta Neuropathologica · PMID 30874984Open reference}2

• Improves separation of amyloid-independent tau biology from AD-targeted cohorts

• Supports stratification of mixed pathology in aging studies

• Helps explain discordance between tau pathology and clinical syndrome severity

Priority research gaps include longitudinal biomarker validation, clinicopathologic prediction models, and intervention studies targeting tau-predominant aging phenotypes.^{3Defining and phenotyping age-related tauopathy in the context of cognitive decline2019 · Acta Neuropathologica · PMID 30874984Open reference}3^{3Defining and phenotyping age-related tauopathy in the context of cognitive decline2019 · Acta Neuropathologica · PMID 30874984Open reference}4

See Also

• Progressive Supranuclear Palsy

• Corticobasal Degeneration

• Tauopathy

• 4R Tauopathy Mechanisms

• Alzheimer’s Disease

Related NeuroWiki Pages

Core CBS/PSP Disorders

• Progressive Supranuclear Palsy (PSP))))))))))))))))))))))

• Corticobasal Degeneration (CBD)

• Corticobasal Syndrome (CBS)

• Primary Age-Related Tauopathy (PART)

• Frontotemporal Dementia (FTD)

Pathobiology and Mechanisms

• Tauopathy

• 4R Tauopathy Mechanism

• Tau Protein Aggregation

• Neuroinflammation in Tauopathy

• Autophagy-Lysosomal Dysfunction in Tauopathy

• Mitochondrial Dysfunction in Tauopathy

Biomarkers and Phenotyping

• Tau PET in CBS/PSP

• MRI Atrophy Patterns in CBS/PSP

• DTI White Matter Changes in CBS/PSP

• PSP Biomarker Framework

Circuit and Cell-Type Context

• Red Nucleus Neurons in PSP

• Subthalamic Nucleus Neurons in PSP

• Globus Pallidus Neurons in CBD

• Striatal Interneurons in CBD

• Locus Coeruleus Neurons in PSP

Therapeutic and Care Pathways

• CBS/PSP Daily Action Plan

• CBS/PSP Rehabilitation Guide

• CBS/PSP Clinical Trials Guide

• CBS/PSP Treatment Rankings

• Lithium for Tauopathy

• Rapamycin for Tauopathy

• TUDCA/UDCA in Neurodegeneration

External Links

• PART - PubMed

• Primary Age-Related Tauopathy - Johns Hopkins

Recent Research (2024-2026)

Recent advances in Primary Age-Related Tauopathy (PART) have focused on understanding disease mechanisms, identifying biomarkers, and developing novel therapeutic approaches. Key developments include:

• Genetic studies: Identification of new genetic risk factors and mechanistic insights

• Biomarker research: Development of diagnostic and prognostic biomarkers

• Therapeutic approaches: Investigation of novel treatment strategies

• Clinical trials: Ongoing Phase I-III trials for new therapies

Allen Brain Atlas Resources

• Allen Brain Atlas - Gene Expression - Search for gene expression data across brain regions

• Allen Brain Atlas - Cell Types - Explore neuronal cell type taxonomy

• Allen Brain Atlas - Aging, Dementia & TBI - Data on aging and traumatic brain injury

• BrainSpan Atlas of the Developing Human Brain - Developmental gene expression data