Frontotemporal Dementia

Complex MONDO:0017276 Pathograph 8 Show in embeddings browser Dementia Neurodegenerative Disease

Frontotemporal Dementia (FTD) is a group of neurodegenerative disorders characterized by progressive deterioration of the frontal and temporal lobes of the brain. It presents with prominent changes in personality, behavior, and/or language, typically with onset before age 65. FTD is associated with abnormal accumulation of tau, TDP-43, or (less commonly) FUS proteins.

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5
Pathophys.
4
Phenotypes
8
Pathograph
3
Genes
2
Medical Actions
4
Subtypes
1
Datasets
5
References
2
Deep Research
🏷

Classifications

Harrison's Part
NEUROLOGIC
Mechanistic Nosology
tauopathy proteotoxic disease
◆

Subtypes

4
Behavioral Variant Frontotemporal Dementia (bvFTD) MONDO:0017160
MAPT hgnc:6893 HUGO Gene Nomenclature Committee (hgnc) Relation: this subtype is caused by variation in this gene This subtype is caused by variation in MAPT (hgnc:6893). hgnc:6893 is a gene from the HUGO Gene Nomenclature Committee. C9orf72 hgnc:28337 HUGO Gene Nomenclature Committee (hgnc) Relation: this subtype is caused by variation in this gene This subtype is caused by variation in C9orf72 (hgnc:28337). hgnc:28337 is a gene from the HUGO Gene Nomenclature Committee.
The most common clinical presentation of FTD, characterized by progressive behavioral and personality change with frontal-lobe-predominant atrophy. Preferentially associated with MAPT mutations, which show earlier onset, prominent disinhibition, stereotyped behaviors, and temporal-predominant atrophy; also a common presentation in C9orf72 carriers, who additionally show psychotic symptoms and paradoxical social warmth.
Show evidence (1 reference)
PMID:26473392 SUPPORT Human Clinical
"MAPT patients were younger than other groups, and showed more frequent behavioural disinhibition, repetitive and stereotyped behaviours, semantic impairment and temporal predominance of atrophy."
Confirms MAPT mutations preferentially produce the behavioral-variant clinical phenotype with early disinhibition and temporal-predominant atrophy.
Semantic Variant Primary Progressive Aphasia (svPPA / Semantic Dementia) MONDO:0010857
A language-predominant FTD syndrome characterized by progressive loss of semantic knowledge (anomia, impaired word comprehension, surface dyslexia) with anterior temporal lobe degeneration. One of the three canonical PPA variants (with nonfluent/agrammatic and logopenic) defined by international consensus criteria. Typically sporadic with underlying TDP-43 type C pathology, showing weaker association with the three major FTD genes than the behavioral or nonfluent variants.
Show evidence (1 reference)
PMID:21325651 SUPPORT Human Clinical
"Criteria for the 3 variants of PPA--nonfluent/agrammatic, semantic, and logopenic--were developed by an international group of PPA investigators who convened on 3 occasions to operationalize earlier published clinical descriptions for PPA subtypes."
Establishes semantic variant PPA as one of the three internationally standardized clinical PPA subtypes within the FTD spectrum.
Nonfluent/Agrammatic Variant Primary Progressive Aphasia (nfvPPA) MONDO:0015059
GRN hgnc:4601 HUGO Gene Nomenclature Committee (hgnc) Relation: this subtype is caused by variation in this gene This subtype is caused by variation in GRN (hgnc:4601). hgnc:4601 is a gene from the HUGO Gene Nomenclature Committee.
A language-predominant FTD syndrome characterized by agrammatism, laborious non-fluent speech, and apraxia of speech, with relatively preserved comprehension. Preferentially associated with GRN mutations (older age at death, TDP-43 type A pathology) and also seen with C9orf72 expansions; non-fluent aphasia links to TDP-43 type A pathology in both groups.
Show evidence (2 references)
PMID:26473392 SUPPORT Human Clinical
"GRN patients were older at death and more likely to present with non-fluent aphasia."
Confirms GRN mutations preferentially produce the nonfluent/agrammatic-aphasia clinical phenotype.
PMID:26473392 SUPPORT Human Clinical
"Non-fluent aphasia was linked to TDP subtype A in both GRN and C9orf72 cases and ALS with subtype B."
Links the nonfluent-aphasia phenotype to TDP-43 type A pathology across both GRN- and C9orf72-associated FTD.
Frontotemporal Dementia with Motor Neuron Disease (FTD-MND / FTD-ALS) MONDO:0017161
C9orf72 hgnc:28337 HUGO Gene Nomenclature Committee (hgnc) Relation: this subtype is caused by variation in this gene This subtype is caused by variation in C9orf72 (hgnc:28337). hgnc:28337 is a gene from the HUGO Gene Nomenclature Committee.
FTD co-occurring with clinical motor neuron disease/ALS, almost exclusively linked to the C9orf72 hexanucleotide repeat expansion. C9orf72-associated ALS-FTD cases show more psychotic symptoms and paradoxical social warmth than MAPT- or GRN-associated FTD, and ALS co-occurrence links to TDP-43 type B pathology.
Show evidence (2 references)
PMID:26473392 SUPPORT Human Clinical
"C9orf72 patients alone showed a co-occurrence of ALS."
Confirms that ALS co-occurrence in this FTD cohort was exclusive to C9orf72 mutation carriers.
PMID:26473392 SUPPORT Human Clinical
"Non-fluent aphasia was linked to TDP subtype A in both GRN and C9orf72 cases and ALS with subtype B."
Links ALS co-occurrence in C9orf72-associated FTD to TDP-43 type B pathology.
⚙

Pathophysiology

5
TDP-43 Proteinopathy
TAR DNA-binding protein of 43 kDa (TDP-43) is the main ubiquitinated protein in tau-negative frontotemporal lobar degeneration (FTLD-TDP), accounting for over 50% of FTD cases. TDP-43 is typically a nuclear protein, and its aggregation and cytoplasmic translocation are thought to represent major pathogenic steps. The abnormal accumulation leads to neuronal dysfunction and death.
neuron CL:0000540 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves neuron (CL:0000540). CL:0000540 is a cell type from the Cell Ontology.
Downstream
Neuronal Death
Behavioral Changes
Aphasia
Show evidence (1 reference)
PMID:19664364 SUPPORT
"TDP-43 is typically a nuclear protein, and its aggregation and cytoplasmic translocation are thought to represent major steps in the pathogenesis of FTLD due to TDP-43 proteinopathy (FTLD-TDP)."
This confirms that TDP-43 aggregation and mislocalization are central to the pathogenesis of FTLD-TDP, a major subtype of frontotemporal dementia.
Tau Proteinopathy
FTLD-tau is characterized by accumulation of hyperphosphorylated tau protein, accounting for approximately 45% of FTD cases. This includes Pick's disease with characteristic Pick bodies. The tau pathology disrupts microtubule function and causes neuronal degeneration primarily in frontal and temporal regions.
neuron CL:0000540 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves neuron (CL:0000540). CL:0000540 is a cell type from the Cell Ontology.
Downstream
Neuronal Death
Behavioral Changes
Aphasia
Show evidence (1 reference)
PMID:21720721 SUPPORT Human Clinical
"PiD is the least common FTLD-tau characterized by neuronal Pick bodies in a stereotypic neuroanatomical distribution."
This confirms Pick's disease (PiD), with its characteristic Pick bodies, as one of the FTLD-tau subtypes underlying the tau proteinopathy arm of FTD.
FUS Proteinopathy
A minority of FTD cases are tau- and TDP-43-negative. Within that heterogeneous group (which also includes CHMP2B-associated FTLD-UPS), the cases whose inclusions are immunoreactive for FUS (fused in sarcoma) constitute FTLD-FUS, completing the TDP-43 / tau / FUS molecular triad underlying FTD.
neuron CL:0000540 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves neuron (CL:0000540). CL:0000540 is a cell type from the Cell Ontology.
Downstream
Neuronal Death
Behavioral Changes
Aphasia
Show evidence (1 reference)
PMID:21603977 SUPPORT Human Clinical
"the discovery that the pathological changes in atypical FTLD with ubiquitinated inclusions, neuronal intermediate filament inclusion disease, and basophilic inclusion body disease are immunoreactive for the fused in sarcoma (FUS) protein, resulting in the creation of a new molecular subgroup (FTLD-FUS)"
Establishes FTLD-FUS as a distinct, tau/TDP-43-negative molecular subgroup of frontotemporal lobar degeneration.
Frontal and Temporal Lobe Atrophy
Progressive neuronal loss and atrophy predominantly affecting the frontal and temporal lobes, with patterns varying by genetic subtype. MAPT mutations show temporal predominance, while GRN and C9orf72 mutations may show more variable patterns. This structural degeneration underlies the behavioral and language deficits.
neuron CL:0000540 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves neuron (CL:0000540). CL:0000540 is a cell type from the Cell Ontology.
Downstream
Behavioral Changes
Aphasia
Show evidence (2 references)
PMID:26473392 SUPPORT
"MAPT patients were younger than other groups, and showed more frequent behavioural disinhibition, repetitive and stereotyped behaviours, semantic impairment and temporal predominance of atrophy."
This demonstrates the genotype-specific patterns of brain atrophy and their relationship to clinical phenotypes in frontotemporal dementia.
PMID:42390534 SUPPORT Human Clinical
"All VRS yielded higher atrophy in bvFTD than in PPD patients. The Orbitofrontal, the Anterior-Temporal, and the Fronto-Insula scales were the strongest discriminators."
Multicenter study identifying specific atrophy patterns (orbitofrontal, anterior-temporal, fronto-insular regions) as diagnostic biomarkers for distinguishing bvFTD from primary psychiatric disorder using visual rating scales.
Neuronal Death
Progressive loss of neurons in frontal and temporal cortices due to protein aggregation toxicity, leading to brain atrophy and functional decline. The neurodegeneration progresses over years to decades, with biomarker changes detectable up to 30 years before symptom onset in genetic cases.
neuron CL:0000540 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves neuron (CL:0000540). CL:0000540 is a cell type from the Cell Ontology.
Show evidence (1 reference)
PMID:30711676 SUPPORT
"We observed that biological changes and intracortical facilitation transmission abnormalities significantly antecede the emergence of clinical symptoms of at least 3 decades."
Supports long presymptomatic neurobiological change in genetic FTD, but does not directly quantify neuronal death in the quoted text.
⬡

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.
Pathograph: causal mechanism network for Frontotemporal Dementia Interactive directed graph showing how pathophysiology mechanisms, phenotypes, genetic factors and variants, experimental models, environmental triggers, and treatments relate through causal and linked edges.
●

Phenotypes

4
Behavioral Changes VERY_FREQUENT Neurological HP:0000708 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Behavioral Changes, annotated with Atypical behavior (HP:0000708). HP:0000708 is a phenotype from the Human Phenotype Ontology.
Prominent behavioral changes including disinhibition, apathy, loss of empathy, compulsive behaviors, and dietary changes. Particularly characteristic of behavioral variant FTD.
Show evidence (1 reference)
PMID:26473392 SUPPORT
"MAPT patients were younger than other groups, and showed more frequent behavioural disinhibition, repetitive and stereotyped behaviours, semantic impairment and temporal predominance of atrophy."
This confirms that behavioral disinhibition and repetitive stereotyped behaviors are core clinical features of genetic FTD, particularly in MAPT mutations.
Aphasia VERY_FREQUENT Neurological HP:0002381 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Aphasia (HP:0002381). HP:0002381 is a phenotype from the Human Phenotype Ontology.
Progressive language impairment, particularly non-fluent aphasia in GRN mutations and semantic variant primary progressive aphasia. Language deficits may be the presenting feature.
Show evidence (1 reference)
PMID:26473392 SUPPORT
"GRN patients were older at death and more likely to present with non-fluent aphasia."
This demonstrates that non-fluent aphasia is a characteristic presenting feature in patients with GRN mutations causing frontotemporal dementia.
Personality Changes VERY_FREQUENT Neurological HP:0000751 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Personality changes (HP:0000751). HP:0000751 is a phenotype from the Human Phenotype Ontology.
Progressive changes in personality including social inappropriateness, loss of emotional warmth, and altered social cognition. C9orf72 patients may paradoxically appear socially warm despite other behavioral changes.
Show evidence (1 reference)
PMID:26473392 SUPPORT
"They showed more psychotic symptoms and irrational behaviour, yet were more often reported clinically as socially appropriate and warm."
This highlights the complex and sometimes paradoxical personality changes in C9orf72-related FTD, where patients may retain apparent social warmth despite significant behavioral dysfunction.
Dementia VERY_FREQUENT Neurological HP:0000726 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Dementia (HP:0000726). HP:0000726 is a phenotype from the Human Phenotype Ontology.
Progressive cognitive decline affecting executive function, social cognition, and behavior, with relatively preserved memory in early stages compared to Alzheimer's disease.
🧬

Genetic Associations

3
MAPT (Mutations cause autosomal dominant FTD with tau pathology)
Gene: MAPT hgnc:6893 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is MAPT (hgnc:6893). hgnc:6893 is a gene from the HUGO Gene Nomenclature Committee.
Show evidence (1 reference)
PMID:26473392 SUPPORT
"MAPT patients were younger than other groups, and showed more frequent behavioural disinhibition, repetitive and stereotyped behaviours, semantic impairment and temporal predominance of atrophy."
This confirms the distinct clinical and anatomical phenotype associated with MAPT mutations in frontotemporal dementia.
GRN (Mutations cause autosomal dominant FTD with TDP-43 pathology)
Gene: GRN hgnc:4601 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is GRN (hgnc:4601). hgnc:4601 is a gene from the HUGO Gene Nomenclature Committee.
Show evidence (2 references)
PMID:26473392 SUPPORT
"GRN patients were older at death and more likely to present with non-fluent aphasia."
This demonstrates the characteristic clinical presentation of GRN-related FTD with language deficits.
PMID:30711676 SUPPORT
"Presymptomatic carriers of GRN and C9orf72 mutations, the most frequent genetic causes of frontotemporal lobar degeneration, represent the optimal target population for the development of disease-modifying drugs."
This confirms GRN as one of the two most common genetic causes of FTD.
C9orf72 (Hexanucleotide repeat expansion causes autosomal dominant FTD, often with ALS)
Gene: C9orf72 hgnc:28337 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is C9orf72 (hgnc:28337). hgnc:28337 is a gene from the HUGO Gene Nomenclature Committee.
Show evidence (2 references)
PMID:26473392 SUPPORT
"C9orf72 patients alone showed a co-occurrence of ALS. They showed more psychotic symptoms and irrational behaviour, yet were more often reported clinically as socially appropriate and warm."
This highlights the distinctive clinical features of C9orf72-related FTD including the frequent association with ALS and unique behavioral profile.
PMID:30711676 SUPPORT
"Presymptomatic carriers of GRN and C9orf72 mutations, the most frequent genetic causes of frontotemporal lobar degeneration, represent the optimal target population for the development of disease-modifying drugs."
This confirms C9orf72 as one of the most common genetic causes of FTD.
💊

Medical Actions

2
Symptomatic Management
Action: Symptomatic TherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Symptomatic Therapy (NCIT:C170740). NCIT:C170740 is a clinical intervention from the NCI Thesaurus. NCIT:C170740
No disease-modifying treatments currently available. Management focuses on behavioral symptoms with selective serotonin reuptake inhibitors for compulsive behaviors and agitation, and non-pharmacological approaches including behavioral interventions and caregiver support.
Speech and Language Therapy
Action: supportive careNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is supportive care (NCIT:C15747). NCIT:C15747 is a clinical intervention from the NCI Thesaurus. Ontology label: Supportive Care NCIT:C15747
Speech therapy interventions for patients with language-variant FTD to maintain communication abilities and quality of life for as long as possible.
🔬

Biochemical Markers

1
NEFL-C1QL2 Projection Neuron Plasma Proteomic Age Gap (Elevated)
Context: Blood-based cell-type-specific aging clock. Plasma proteins are mapped to their putative cell of origin using Human Protein Atlas single-cell transcriptomic data, and a machine-learning model estimates that cell type's biological age; the age gap is the difference between that estimate and chronological age. "Extreme" agers are those in the upper tail of the age-gap distribution.
Pathograph Readouts
Predicts Neuronal Death Positive Prognostic
An elevated NEFL-C1QL2 projection neuron age gap predicts incident frontotemporal dementia. The NEFL component is an established axonal-injury marker in FTD, which is what anchors the readout to the neurodegeneration arm rather than leaving it an unanchored risk score.
Show evidence (1 reference)
PMID:42297981 SUPPORT Human Clinical
"extreme aging in NEFL-C1QL2 projection neurons demonstrated the strongest prognostic value"
Supports treating the age gap as a prognostic readout anticipating clinical frontotemporal dementia.
Correlates With Frontal and Temporal Lobe Atrophy Positive Prognostic
C1QL2 is enriched in the temporo-limbic structures that frontotemporal lobar degeneration targets, which is the authors' basis for reading this signature against the regional atrophy arm. This is a regional-expression argument, not a measured correlation with imaged atrophy.
Show evidence (1 reference)
PMID:42297981 SUPPORT Human Clinical
"C1QL2 is a synaptic organizer known to be prominent in temporo-limbic structures vulnerable to frontotemporal lobar degeneration"
Gives the regional-vulnerability rationale connecting the signature to the frontal and temporal atrophy node.
Show evidence (2 references)
PMID:42297981 SUPPORT Human Clinical
"extreme aging in NEFL-C1QL2 projection neurons demonstrated the strongest prognostic value"
Establishes this signature as the leading cellular-aging predictor of incident frontotemporal dementia among the cell types tested.
PMID:42297981 SUPPORT Human Clinical
"NEFL is a widely recognized biomarker of axonal injury, often markedly raised in FTD, while C1QL2 is a synaptic organizer known to be prominent in temporo-limbic structures vulnerable to frontotemporal lobar degeneration"
The authors' justification for both the relabelling and the disease relevance: one marker of axonal injury already established in FTD, one synaptic gene enriched in the regions FTLD targets.
📊

Related Datasets

1
Expression data from postmortem human brain samples with and without FTLD-U geo:GSE13162
Microarray expression profiling of frontal cortex, hippocampus, and cerebellum from FTLD-U and control brains.
human MICROARRAY n=56
brain tissue UBERON:0000955 Uberon multi-species anatomy ontology (UBERON) Relation: this dataset samples this sample type This dataset samples brain tissue, annotated with brain (UBERON:0000955). UBERON:0000955 is a sample type from the Uberon multi-species anatomy ontology.
Conditions: frontotemporal lobar degeneration with ubiquitin-positive inclusions control brain tissue
Includes 31 FTLD-U and 25 control samples.
{ }

Source YAML

click to show 
name: Frontotemporal Dementia
creation_date: '2025-12-23T16:19:20Z'
description: >
  Frontotemporal Dementia (FTD) is a group of neurodegenerative disorders characterized
  by progressive deterioration of the frontal and temporal lobes of the brain. It
  presents
  with prominent changes in personality, behavior, and/or language, typically with
  onset
  before age 65. FTD is associated with abnormal accumulation of tau, TDP-43, or (less commonly) FUS proteins.
category: Complex
disease_term:
  preferred_term: frontotemporal dementia
  term:
    id: MONDO:0017276
    label: frontotemporal dementia
parents:
- Dementia
- Neurodegenerative Disease
has_subtypes:
- name: Behavioral Variant FTD
  display_name: Behavioral Variant Frontotemporal Dementia (bvFTD)
  subtype_term:
    preferred_term: behavioral variant of frontotemporal dementia
    term:
      id: MONDO:0017160
      label: behavioral variant of frontotemporal dementia
  description: >
    The most common clinical presentation of FTD, characterized by progressive
    behavioral and personality change with frontal-lobe-predominant atrophy.
    Preferentially associated with MAPT mutations, which show earlier onset,
    prominent disinhibition, stereotyped behaviors, and temporal-predominant
    atrophy; also a common presentation in C9orf72 carriers, who additionally
    show psychotic symptoms and paradoxical social warmth.
  genes:
  - preferred_term: MAPT
    term:
      id: hgnc:6893
      label: MAPT
  - preferred_term: C9orf72
    term:
      id: hgnc:28337
      label: C9orf72
  evidence:
  - reference: PMID:26473392
    reference_title: "Distinct clinical and pathological phenotypes in frontotemporal dementia associated with MAPT, PGRN and C9orf72 mutations."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: MAPT patients were younger than other groups, and showed more frequent behavioural disinhibition, repetitive and stereotyped behaviours, semantic impairment and temporal predominance of atrophy.
    explanation: Confirms MAPT mutations preferentially produce the behavioral-variant clinical phenotype with early disinhibition and temporal-predominant atrophy.
- name: Semantic Variant PPA
  display_name: Semantic Variant Primary Progressive Aphasia (svPPA / Semantic Dementia)
  subtype_term:
    preferred_term: semantic dementia
    term:
      id: MONDO:0010857
      label: semantic dementia
  description: >
    A language-predominant FTD syndrome characterized by progressive loss of
    semantic knowledge (anomia, impaired word comprehension, surface dyslexia)
    with anterior temporal lobe degeneration. One of the three canonical PPA
    variants (with nonfluent/agrammatic and logopenic) defined by international
    consensus criteria. Typically sporadic with underlying TDP-43 type C
    pathology, showing weaker association with the three major FTD genes than
    the behavioral or nonfluent variants.
  evidence:
  - reference: PMID:21325651
    reference_title: "Classification of primary progressive aphasia and its variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Criteria for the 3 variants of PPA--nonfluent/agrammatic, semantic, and logopenic--were developed by an international group of PPA investigators who convened on 3 occasions to operationalize earlier published clinical descriptions for PPA subtypes.
    explanation: Establishes semantic variant PPA as one of the three internationally standardized clinical PPA subtypes within the FTD spectrum.
- name: Nonfluent Variant PPA
  display_name: Nonfluent/Agrammatic Variant Primary Progressive Aphasia (nfvPPA)
  subtype_term:
    preferred_term: progressive non-fluent aphasia
    term:
      id: MONDO:0015059
      label: progressive non-fluent aphasia
  description: >
    A language-predominant FTD syndrome characterized by agrammatism, laborious
    non-fluent speech, and apraxia of speech, with relatively preserved
    comprehension. Preferentially associated with GRN mutations (older age at
    death, TDP-43 type A pathology) and also seen with C9orf72 expansions;
    non-fluent aphasia links to TDP-43 type A pathology in both groups.
  genes:
  - preferred_term: GRN
    term:
      id: hgnc:4601
      label: GRN
  evidence:
  - reference: PMID:26473392
    reference_title: "Distinct clinical and pathological phenotypes in frontotemporal dementia associated with MAPT, PGRN and C9orf72 mutations."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: GRN patients were older at death and more likely to present with non-fluent aphasia.
    explanation: Confirms GRN mutations preferentially produce the nonfluent/agrammatic-aphasia clinical phenotype.
  - reference: PMID:26473392
    reference_title: "Distinct clinical and pathological phenotypes in frontotemporal dementia associated with MAPT, PGRN and C9orf72 mutations."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Non-fluent aphasia was linked to TDP subtype A in both GRN and C9orf72 cases and ALS with subtype B.
    explanation: Links the nonfluent-aphasia phenotype to TDP-43 type A pathology across both GRN- and C9orf72-associated FTD.
- name: FTD with Motor Neuron Disease
  display_name: Frontotemporal Dementia with Motor Neuron Disease (FTD-MND / FTD-ALS)
  subtype_term:
    preferred_term: frontotemporal dementia with motor neuron disease
    term:
      id: MONDO:0017161
      label: frontotemporal dementia with motor neuron disease
  description: >
    FTD co-occurring with clinical motor neuron disease/ALS, almost exclusively
    linked to the C9orf72 hexanucleotide repeat expansion. C9orf72-associated
    ALS-FTD cases show more psychotic symptoms and paradoxical social warmth
    than MAPT- or GRN-associated FTD, and ALS co-occurrence links to TDP-43
    type B pathology.
  genes:
  - preferred_term: C9orf72
    term:
      id: hgnc:28337
      label: C9orf72
  evidence:
  - reference: PMID:26473392
    reference_title: "Distinct clinical and pathological phenotypes in frontotemporal dementia associated with MAPT, PGRN and C9orf72 mutations."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: C9orf72 patients alone showed a co-occurrence of ALS.
    explanation: Confirms that ALS co-occurrence in this FTD cohort was exclusive to C9orf72 mutation carriers.
  - reference: PMID:26473392
    reference_title: "Distinct clinical and pathological phenotypes in frontotemporal dementia associated with MAPT, PGRN and C9orf72 mutations."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Non-fluent aphasia was linked to TDP subtype A in both GRN and C9orf72 cases and ALS with subtype B.
    explanation: Links ALS co-occurrence in C9orf72-associated FTD to TDP-43 type B pathology.
pathophysiology:
- name: TDP-43 Proteinopathy
  description: >
    TAR DNA-binding protein of 43 kDa (TDP-43) is the main ubiquitinated protein
    in tau-negative frontotemporal lobar degeneration (FTLD-TDP), accounting for
    over 50% of FTD cases. TDP-43 is typically a nuclear protein, and its aggregation
    and cytoplasmic translocation are thought to represent major pathogenic steps.
    The abnormal accumulation leads to neuronal dysfunction and death.
  cell_types:
  - preferred_term: neuron
    term:
      id: CL:0000540
      label: neuron
  downstream:
  - target: Neuronal Death
  - target: Behavioral Changes
  - target: Aphasia
  evidence:
  - reference: PMID:19664364
    reference_title: "TDP-43 and frontotemporal dementia."
    supports: SUPPORT
    snippet: TDP-43 is typically a nuclear protein, and its aggregation and cytoplasmic translocation are thought to represent major steps in the pathogenesis of FTLD due to TDP-43 proteinopathy (FTLD-TDP).
    explanation: This confirms that TDP-43 aggregation and mislocalization are central to the pathogenesis of FTLD-TDP, a major subtype of frontotemporal dementia.
- name: Tau Proteinopathy
  description: >
    FTLD-tau is characterized by accumulation of hyperphosphorylated tau protein,
    accounting for approximately 45% of FTD cases. This includes Pick's disease
    with characteristic Pick bodies. The tau pathology disrupts microtubule function
    and causes neuronal degeneration primarily in frontal and temporal regions.
  cell_types:
  - preferred_term: neuron
    term:
      id: CL:0000540
      label: neuron
  downstream:
  - target: Neuronal Death
  - target: Behavioral Changes
  - target: Aphasia
  evidence:
  - reference: PMID:21720721
    reference_title: "Neuropathology of frontotemporal lobar degeneration-tau (FTLD-tau)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: PiD is the least common FTLD-tau characterized by neuronal Pick bodies in a stereotypic neuroanatomical distribution.
    explanation: This confirms Pick's disease (PiD), with its characteristic Pick bodies, as one of the FTLD-tau subtypes underlying the tau proteinopathy arm of FTD.
- name: FUS Proteinopathy
  description: >
    A minority of FTD cases are tau- and TDP-43-negative. Within that
    heterogeneous group (which also includes CHMP2B-associated FTLD-UPS), the
    cases whose inclusions are immunoreactive for FUS (fused in sarcoma)
    constitute FTLD-FUS, completing the TDP-43 / tau / FUS molecular triad
    underlying FTD.
  biological_scale: MOLECULAR
  cell_types:
  - preferred_term: neuron
    term:
      id: CL:0000540
      label: neuron
  downstream:
  - target: Neuronal Death
  - target: Behavioral Changes
  - target: Aphasia
  evidence:
  - reference: PMID:21603977
    reference_title: "Novel types of frontotemporal lobar degeneration: beyond tau and TDP-43."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: the discovery that the pathological changes in atypical FTLD with ubiquitinated inclusions, neuronal intermediate filament inclusion disease, and basophilic inclusion body disease are immunoreactive for the fused in sarcoma (FUS) protein, resulting in the creation of a new molecular subgroup (FTLD-FUS)
    explanation: Establishes FTLD-FUS as a distinct, tau/TDP-43-negative molecular subgroup of frontotemporal lobar degeneration.
- name: Frontal and Temporal Lobe Atrophy
  description: >
    Progressive neuronal loss and atrophy predominantly affecting the frontal and
    temporal lobes, with patterns varying by genetic subtype. MAPT mutations show
    temporal predominance, while GRN and C9orf72 mutations may show more variable
    patterns. This structural degeneration underlies the behavioral and language deficits.
  cell_types:
  - preferred_term: neuron
    term:
      id: CL:0000540
      label: neuron
  downstream:
  - target: Behavioral Changes
  - target: Aphasia
  evidence:
  - reference: PMID:26473392
    reference_title: "Distinct clinical and pathological phenotypes in frontotemporal dementia associated with MAPT, PGRN and C9orf72 mutations."
    supports: SUPPORT
    snippet: MAPT patients were younger than other groups, and showed more frequent behavioural disinhibition, repetitive and stereotyped behaviours, semantic impairment and temporal predominance of atrophy.
    explanation: This demonstrates the genotype-specific patterns of brain atrophy and their relationship to clinical phenotypes in frontotemporal dementia.
  - reference: PMID:42390534
    reference_title: "Visual rating scales of atrophy differentiate sporadic behavioral variant frontotemporal dementia from primary psychiatric disorder: DIPPA study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: All VRS yielded higher atrophy in bvFTD than in PPD patients. The Orbitofrontal, the Anterior-Temporal, and the Fronto-Insula scales were the strongest discriminators.
    explanation: Multicenter study identifying specific atrophy patterns (orbitofrontal, anterior-temporal, fronto-insular regions) as diagnostic biomarkers for distinguishing bvFTD from primary psychiatric disorder using visual rating scales.
- name: Neuronal Death
  description: >
    Progressive loss of neurons in frontal and temporal cortices due to protein
    aggregation toxicity, leading to brain atrophy and functional decline. The
    neurodegeneration progresses over years to decades, with biomarker changes
    detectable up to 30 years before symptom onset in genetic cases.
  cell_types:
  - preferred_term: neuron
    term:
      id: CL:0000540
      label: neuron
  evidence:
  - reference: PMID:30711676
    reference_title: "Clinical and biomarker changes in presymptomatic genetic frontotemporal dementia."
    supports: SUPPORT
    snippet: We observed that biological changes and intracortical facilitation transmission abnormalities significantly antecede the emergence of clinical symptoms of at least 3 decades.
    explanation: Supports long presymptomatic neurobiological change in genetic FTD, but does not directly quantify neuronal death in the quoted text.
phenotypes:
- category: Neurological
  name: Behavioral Changes
  phenotype_term:
    preferred_term: Behavioral Changes
    term:
      id: HP:0000708
      label: Atypical behavior
  frequency: VERY_FREQUENT
  diagnostic: true
  notes: Prominent behavioral changes including disinhibition, apathy, loss of empathy, compulsive behaviors, and dietary changes. Particularly characteristic of behavioral variant FTD.
  evidence:
  - reference: PMID:26473392
    reference_title: "Distinct clinical and pathological phenotypes in frontotemporal dementia associated with MAPT, PGRN and C9orf72 mutations."
    supports: SUPPORT
    snippet: MAPT patients were younger than other groups, and showed more frequent behavioural disinhibition, repetitive and stereotyped behaviours, semantic impairment and temporal predominance of atrophy.
    explanation: This confirms that behavioral disinhibition and repetitive stereotyped behaviors are core clinical features of genetic FTD, particularly in MAPT mutations.
- category: Neurological
  name: Aphasia
  frequency: VERY_FREQUENT
  diagnostic: true
  notes: Progressive language impairment, particularly non-fluent aphasia in GRN mutations and semantic variant primary progressive aphasia. Language deficits may be the presenting feature.
  evidence:
  - reference: PMID:26473392
    reference_title: "Distinct clinical and pathological phenotypes in frontotemporal dementia associated with MAPT, PGRN and C9orf72 mutations."
    supports: SUPPORT
    snippet: GRN patients were older at death and more likely to present with non-fluent aphasia.
    explanation: This demonstrates that non-fluent aphasia is a characteristic presenting feature in patients with GRN mutations causing frontotemporal dementia.
  phenotype_term:
    preferred_term: Aphasia
    term:
      id: HP:0002381
      label: Aphasia
- category: Neurological
  name: Personality Changes
  frequency: VERY_FREQUENT
  diagnostic: true
  notes: Progressive changes in personality including social inappropriateness, loss of emotional warmth, and altered social cognition. C9orf72 patients may paradoxically appear socially warm despite other behavioral changes.
  evidence:
  - reference: PMID:26473392
    reference_title: "Distinct clinical and pathological phenotypes in frontotemporal dementia associated with MAPT, PGRN and C9orf72 mutations."
    supports: SUPPORT
    snippet: They showed more psychotic symptoms and irrational behaviour, yet were more often reported clinically as socially appropriate and warm.
    explanation: This highlights the complex and sometimes paradoxical personality changes in C9orf72-related FTD, where patients may retain apparent social warmth despite significant behavioral dysfunction.
  phenotype_term:
    preferred_term: Personality changes
    term:
      id: HP:0000751
      label: Personality changes
- category: Neurological
  name: Dementia
  frequency: VERY_FREQUENT
  diagnostic: true
  notes: Progressive cognitive decline affecting executive function, social cognition, and behavior, with relatively preserved memory in early stages compared to Alzheimer's disease.
  phenotype_term:
    preferred_term: Dementia
    term:
      id: HP:0000726
      label: Dementia
biochemical:
- name: NEFL-C1QL2 Projection Neuron Plasma Proteomic Age Gap
  biomarker_term:
    preferred_term: NEFL-C1QL2 projection neuron plasma proteomic aging clock (age gap)
    term:
      id: NCIT:C97139
      label: Proteomic Profile
  presence: Elevated
  context: >-
    Blood-based cell-type-specific aging clock. Plasma proteins are mapped to
    their putative cell of origin using Human Protein Atlas single-cell
    transcriptomic data, and a machine-learning model estimates that cell type's
    biological age; the age gap is the difference between that estimate and
    chronological age. "Extreme" agers are those in the upper tail of the age-gap
    distribution.
  cell_types:
  - preferred_term: NEFL-C1QL2 projection neuron
    term:
      id: CL:0000540
      label: neuron
  notes: >-
    Read the cell-type label carefully. The Human Protein Atlas catalogues this
    population as "horizontal cell", a retinal interneuron type; the authors
    renamed it NEFL-C1QL2 projection neuron because the two defining transcripts
    point at a projection-neuron identity rather than a retinal one. Curated
    under the authors' relabelling, with CL:0000540 neuron as the only defensible
    binding - there is no CL term for this population, and binding it to the
    retinal horizontal cell would import an assignment the authors explicitly
    rejected. This makes the entry a worked example of the probabilistic
    protein-to-cell-type mapping being the weakest link in these clocks. It was
    the strongest cellular-aging predictor of incident frontotemporal dementia
    (HR 3.03, 95% CI 2.47-3.72), followed by microglia (HR 2.84, 95% CI
    2.33-3.47), and also the strongest cross-sectional association with
    prevalent FTD in the GNPC cohort (n = 199 FTD cases).
  evidence:
  - reference: PMID:42297981
    reference_title: "Plasma proteomic signatures of cellular aging predict human disease."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: extreme aging in NEFL-C1QL2 projection neurons demonstrated the strongest prognostic value
    explanation: >-
      Establishes this signature as the leading cellular-aging predictor of
      incident frontotemporal dementia among the cell types tested.
  - reference: PMID:42297981
    reference_title: "Plasma proteomic signatures of cellular aging predict human disease."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: NEFL is a widely recognized biomarker of axonal injury, often markedly raised in FTD, while C1QL2 is a synaptic organizer known to be prominent in temporo-limbic structures vulnerable to frontotemporal lobar degeneration
    explanation: >-
      The authors' justification for both the relabelling and the disease
      relevance: one marker of axonal injury already established in FTD, one
      synaptic gene enriched in the regions FTLD targets.
  readouts:
  - target: Neuronal Death
    relationship: PREDICTS
    direction: POSITIVE
    endpoint_context: PROGNOSTIC
    interpretation: >-
      An elevated NEFL-C1QL2 projection neuron age gap predicts incident
      frontotemporal dementia. The NEFL component is an established axonal-injury
      marker in FTD, which is what anchors the readout to the neurodegeneration
      arm rather than leaving it an unanchored risk score.
    evidence:
    - reference: PMID:42297981
      reference_title: "Plasma proteomic signatures of cellular aging predict human disease."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: extreme aging in NEFL-C1QL2 projection neurons demonstrated the strongest prognostic value
      explanation: >-
        Supports treating the age gap as a prognostic readout anticipating
        clinical frontotemporal dementia.
  - target: Frontal and Temporal Lobe Atrophy
    relationship: CORRELATES_WITH
    direction: POSITIVE
    endpoint_context: PROGNOSTIC
    interpretation: >-
      C1QL2 is enriched in the temporo-limbic structures that frontotemporal
      lobar degeneration targets, which is the authors' basis for reading this
      signature against the regional atrophy arm. This is a regional-expression
      argument, not a measured correlation with imaged atrophy.
    evidence:
    - reference: PMID:42297981
      reference_title: "Plasma proteomic signatures of cellular aging predict human disease."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: C1QL2 is a synaptic organizer known to be prominent in temporo-limbic structures vulnerable to frontotemporal lobar degeneration
      explanation: >-
        Gives the regional-vulnerability rationale connecting the signature to
        the frontal and temporal atrophy node.
genetic:
- name: MAPT
  gene_term:
    preferred_term: MAPT
    term:
      id: hgnc:6893
      label: MAPT
  association: Mutations cause autosomal dominant FTD with tau pathology
  notes: Microtubule-associated protein tau gene on chromosome 17q21. Mutations lead to FTLD-tau pathology. Patients show earlier onset, prominent behavioral disinhibition, stereotyped behaviors, and temporal lobe predominance of atrophy.
  evidence:
  - reference: PMID:26473392
    reference_title: "Distinct clinical and pathological phenotypes in frontotemporal dementia associated with MAPT, PGRN and C9orf72 mutations."
    supports: SUPPORT
    snippet: MAPT patients were younger than other groups, and showed more frequent behavioural disinhibition, repetitive and stereotyped behaviours, semantic impairment and temporal predominance of atrophy.
    explanation: This confirms the distinct clinical and anatomical phenotype associated with MAPT mutations in frontotemporal dementia.
- name: GRN
  gene_term:
    preferred_term: GRN
    term:
      id: hgnc:4601
      label: GRN
  association: Mutations cause autosomal dominant FTD with TDP-43 pathology
  notes: Progranulin gene on chromosome 17q21. Haploinsufficiency leads to FTLD-TDP pathology. Patients more likely to present with non-fluent aphasia and are older at symptom onset. GRN and C9orf72 are the most frequent genetic causes.
  evidence:
  - reference: PMID:26473392
    reference_title: "Distinct clinical and pathological phenotypes in frontotemporal dementia associated with MAPT, PGRN and C9orf72 mutations."
    supports: SUPPORT
    snippet: GRN patients were older at death and more likely to present with non-fluent aphasia.
    explanation: This demonstrates the characteristic clinical presentation of GRN-related FTD with language deficits.
  - reference: PMID:30711676
    reference_title: "Clinical and biomarker changes in presymptomatic genetic frontotemporal dementia."
    supports: SUPPORT
    snippet: Presymptomatic carriers of GRN and C9orf72 mutations, the most frequent genetic causes of frontotemporal lobar degeneration, represent the optimal target population for the development of disease-modifying drugs.
    explanation: This confirms GRN as one of the two most common genetic causes of FTD.
- name: C9orf72
  gene_term:
    preferred_term: C9orf72
    term:
      id: hgnc:28337
      label: C9orf72
  association: Hexanucleotide repeat expansion causes autosomal dominant FTD, often with ALS
  notes: Hexanucleotide (GGGGCC) repeat expansion on chromosome 9p21. Most common genetic cause of FTD. Causes FTLD-TDP pathology. Unique features include co-occurrence with ALS, psychotic symptoms, and paradoxically preserved social warmth.
  evidence:
  - reference: PMID:26473392
    reference_title: "Distinct clinical and pathological phenotypes in frontotemporal dementia associated with MAPT, PGRN and C9orf72 mutations."
    supports: SUPPORT
    snippet: C9orf72 patients alone showed a co-occurrence of ALS. They showed more psychotic symptoms and irrational behaviour, yet were more often reported clinically as socially appropriate and warm.
    explanation: This highlights the distinctive clinical features of C9orf72-related FTD including the frequent association with ALS and unique behavioral profile.
  - reference: PMID:30711676
    reference_title: "Clinical and biomarker changes in presymptomatic genetic frontotemporal dementia."
    supports: SUPPORT
    snippet: Presymptomatic carriers of GRN and C9orf72 mutations, the most frequent genetic causes of frontotemporal lobar degeneration, represent the optimal target population for the development of disease-modifying drugs.
    explanation: This confirms C9orf72 as one of the most common genetic causes of FTD.
treatments:
- name: Symptomatic Management
  description: No disease-modifying treatments currently available. Management focuses on behavioral symptoms with selective serotonin reuptake inhibitors for compulsive behaviors and agitation, and non-pharmacological approaches including behavioral interventions and caregiver support.
  treatment_term:
    preferred_term: Symptomatic Therapy
    term:
      id: NCIT:C170740
      label: Symptomatic Therapy
- name: Speech and Language Therapy
  description: Speech therapy interventions for patients with language-variant FTD to maintain communication abilities and quality of life for as long as possible.
  treatment_term:
    preferred_term: supportive care
    term:
      id: NCIT:C15747
      label: Supportive Care
classifications:
  harrisons_chapter:
  - classification_value: NEUROLOGIC
  mechanistic_category:
  - classification_value: tauopathy
  - classification_value: proteotoxic disease
datasets:
- accession: geo:GSE13162
  title: Expression data from postmortem human brain samples with and without FTLD-U
  description: Microarray expression profiling of frontal cortex, hippocampus, and cerebellum from FTLD-U and control brains.
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  data_type: MICROARRAY
  sample_types:
  - preferred_term: brain tissue
    tissue_term:
      preferred_term: brain
      term:
        id: UBERON:0000955
        label: brain
  sample_count: 56
  conditions:
  - frontotemporal lobar degeneration with ubiquitin-positive inclusions
  - control brain tissue
  notes: Includes 31 FTLD-U and 25 control samples.
references:
- reference: DOI:10.1093/brain/awae074
  title: 'Synaptopathy: presynaptic convergence in frontotemporal dementia and amyotrophic lateral sclerosis'
  findings: []
- reference: DOI:10.1101/2024.02.09.579529
  title: Alterations in Lysosomal, Glial and Neurodegenerative Biomarkers in Patients with Sporadic and Genetic Forms of Frontotemporal Dementia
  findings: []
- reference: DOI:10.1186/s12974-024-03039-1
  title: Progranulin haploinsufficiency mediates cytoplasmic TDP-43 aggregation with lysosomal abnormalities in human microglia
  findings: []
- reference: DOI:10.1186/s40035-024-00429-6
  title: 'Tau in neurodegenerative diseases: molecular mechanisms, biomarkers, and therapeutic strategies'
  findings: []
- reference: DOI:10.21203/rs.3.rs-4103685/v1
  title: Large-scale network analysis of the cerebrospinal fluid proteome identifies molecular signatures of frontotemporal lobar degeneration
  findings: []
📚

References & Deep Research

References

5
DOI:10.1093/brain/awae074
Synaptopathy: presynaptic convergence in frontotemporal dementia and amyotrophic lateral sclerosis
No top-level findings curated for this source.
DOI:10.1101/2024.02.09.579529
Alterations in Lysosomal, Glial and Neurodegenerative Biomarkers in Patients with Sporadic and Genetic Forms of Frontotemporal Dementia
No top-level findings curated for this source.
DOI:10.1186/s12974-024-03039-1
Progranulin haploinsufficiency mediates cytoplasmic TDP-43 aggregation with lysosomal abnormalities in human microglia
No top-level findings curated for this source.
DOI:10.1186/s40035-024-00429-6
Tau in neurodegenerative diseases: molecular mechanisms, biomarkers, and therapeutic strategies
No top-level findings curated for this source.
DOI:10.21203/rs.3.rs-4103685/v1
Large-scale network analysis of the cerebrospinal fluid proteome identifies molecular signatures of frontotemporal lobar degeneration
No top-level findings curated for this source.

Deep Research

2
Disorder ▸

Disorder

  • Name: Frontotemporal Dementia
  • Category: Complex
  • Existing deep-research providers: falcon
  • Existing evidence reference count in YAML: 16

Key Pathophysiology Nodes

  • TDP-43 Proteinopathy
  • Tau Proteinopathy
  • Frontal and Temporal Lobe Atrophy
  • Neuronal Death
  • Deep research literature mapping

Citation Inventory (for evidence mapping)

  • DOI:10.1093/brain/awae074
  • DOI:10.1101/2024.02.09.579529
  • DOI:10.1186/s12974-024-03039-1
  • DOI:10.1186/s40035-024-00429-6
  • DOI:10.15496/publikation-94419
  • DOI:10.21203/rs.3.rs-4103685/v1
Falcon ▸
Pathophysiology description
Edison Scientific Literature 23 citations 2026-02-01T12:53:11.362853

Pathophysiology description Frontotemporal dementia (FTD) encompasses frontotemporal lobar degeneration (FTLD) driven by distinct proteinopathies and convergent cellular stress pathways. The principal pathological classes are FTLD–TDP (abnormal TDP-43), FTLD–tau (abnormal MAPT/tau), and less commonly FTLD–FUS (abnormal FUS/FET proteins). Across genetic and sporadic forms, early synaptic failure—particularly at the presynapse—emerges as a convergent mechanism, followed by progressive neuronal loss and network disintegration in frontal and temporal cortices (paralimbic fronto–insular–striatal circuits) (overview; proportions and convergence on presynaptic dysfunction) (https://doi.org/10.1093/brain/awae074, Mar 2024) (clayton2024synaptopathypresynapticconvergence pages 1-2). Molecularly, risk genes and causal mutations perturb proteostasis (aggregation, phase transitions), RNA metabolism (splicing/transport), autophagy–lysosomal homeostasis, nucleocytoplasmic transport, and innate immune signaling. These processes interact: genetic and proteostatic stressors (e.g., C9orf72 repeat expansions, GRN haploinsufficiency, TMEM106B variation) drive TDP-43 dysfunction and synaptic failure; MAPT mutations drive tau misfolding with axonal and synaptic compromise; and glial activation amplifies neurodegeneration (https://doi.org/10.1186/s40035-024-00429-6 is a tau-focused background review; mechanistic points here from cited sources below) (huber2024mechanismsofneurodegeneration pages 57-60, saloner2025largescalenetworkanalysis pages 1-7, hsiaonakamoto2024alterationsinlysosomal pages 1-5, huber2024mechanismsofneurodegenerationa pages 79-82).

Recent systems–level CSF proteomics across autosomal-dominant FTLD (C9orf72, GRN, MAPT) shows increased RNA-splicing modules (notably in C9orf72, GRN), increased extracellular matrix modules (MAPT), and decreased synaptic/neuronal and autophagy modules, aligning in vivo fluid signatures with core mechanisms and suggesting hub proteins as potential biomarkers/targets (https://doi.org/10.21203/rs.3.rs-4103685/v1, Mar 2025) (saloner2025largescalenetworkanalysis pages 1-7).

1) Core Pathophysiology - Primary mechanisms - Proteinopathies: FTLD–TDP (~about half of cases), FTLD–tau (large fraction), FTLD–FUS (~minority) (synaptopathy review; mechanistic overview) (clayton2024synaptopathypresynapticconvergence pages 1-2, huber2024mechanismsofneurodegeneration pages 57-60). - Synaptic dysfunction: Early, convergent presynaptic deficits in vesicle priming, recycling, and local translation; TDP-43 loss-of-function reduces UNC13A and impairs priming, linking RNA-binding protein pathology to synaptic failure (https://doi.org/10.1093/brain/awae074, 2024; mechanistic synthesis) (clayton2024synaptopathypresynapticconvergence pages 1-2, huber2024mechanismsofneurodegeneration pages 57-60, huber2024mechanismsofneurodegenerationb pages 57-60). - Autophagy–lysosome dysfunction: GRN haploinsufficiency and TMEM106B risk alleles disrupt autophagosome–lysosome maturation, acidification and cargo clearance; in FTLD, autophagy modules are reduced in CSF network analyses (https://doi.org/10.1186/s12974-024-03039-1, Feb 2024; https://doi.org/10.21203/rs.3.rs-4103685/v1, Mar 2025) (sung2024progranulinhaploinsufficiencymediates pages 1-2, huber2024mechanismsofneurodegeneration pages 57-60, saloner2025largescalenetworkanalysis pages 1-7). - Nucleocytoplasmic transport impairment: Particularly in C9orf72 repeat expansion disease (loss-of-function and toxic gain-of-function via RNA foci and dipeptide repeat proteins) with downstream TDP-43 dyshomeostasis (https://doi.org/10.21203/rs.3.rs-4103685/v1, Mar 2025) (saloner2025largescalenetworkanalysis pages 1-7). - Neuroinflammation: Microglial and astrocytic activation; in GRN-related FTD, microglia show TDP-43 cytoplasmic aggregation with lysosomal abnormalities and complement C1q activation; glial biomarkers are elevated in biofluids (https://doi.org/10.1186/s12974-024-03039-1, Feb 2024; biofluid/tissue biomarker study) (sung2024progranulinhaploinsufficiencymediates pages 1-2, hsiaonakamoto2024alterationsinlysosomal pages 1-5, hsiaonakamoto2024alterationsinlysosomal pages 30-33).

  • Dysregulated pathways
  • RNA splicing/processing, synaptic transmission, autophagy/lysosome, extracellular matrix remodeling; decreased synaptic and autophagy modules with increased RNA-splicing signatures in FTLD CSF proteomes (https://doi.org/10.21203/rs.3.rs-4103685/v1, Mar 2025) (saloner2025largescalenetworkanalysis pages 1-7).

  • TMEM106B–lysosome axis modulates TDP-43 dysfunction and C9orf72 DPR burden; UNC13A–synapse axis mediates TDP-43 loss-of-function at the presynapse (mechanistic consolidation) (huber2024mechanismsofneurodegeneration pages 57-60, huber2024mechanismsofneurodegenerationb pages 57-60, huber2024mechanismsofneurodegenerationa pages 57-60).

  • Cellular processes affected

  • Presynaptic vesicle priming/recycling, local translation, long-range axonal transport; autophagosome–lysosome fusion and acidification; nucleocytoplasmic shuttling; complement-mediated synapse/glia crosstalk (clayton2024synaptopathypresynapticconvergence pages 1-2, huber2024mechanismsofneurodegeneration pages 57-60, sung2024progranulinhaploinsufficiencymediates pages 1-2, hsiaonakamoto2024alterationsinlysosomal pages 1-5).

2) Key Molecular Players - Genes/Proteins (HGNC symbols) - GRN (progranulin): Haploinsufficiency causes lysosomal dysfunction and microglial activation; human microglia from GRN-FTD show cytoplasmic TDP-43 aggregation, lipid droplet accumulation, and profound lysosomal abnormalities with complement C1q activation (https://doi.org/10.1186/s12974-024-03039-1, Feb 2024) (sung2024progranulinhaploinsufficiencymediates pages 1-2). - C9orf72: Hexanucleotide repeat expansions cause combined loss-of-function and gain-of-function (RNA foci, dipeptide-repeat proteins) that impair RNA metabolism, nucleocytoplasmic transport, proteostasis and lead to TDP-43 aggregation (https://doi.org/10.21203/rs.3.rs-4103685/v1, Mar 2025) (saloner2025largescalenetworkanalysis pages 1-7). - MAPT (tau): Mutations drive tau aggregation, extracellular matrix and synaptic signaling alterations (CSF proteomics) and axonal/synaptic compromise in FTLD–tau (https://doi.org/10.21203/rs.3.rs-4103685/v1, Mar 2025) (saloner2025largescalenetworkanalysis pages 1-7). - TARDBP (TDP-43): Aggregation and nuclear loss-of-function disrupt RNA splicing/transport; presynaptic effects via UNC13A dysregulation (review evidence) (huber2024mechanismsofneurodegeneration pages 57-60, clayton2024synaptopathypresynapticconvergence pages 1-2). - FUS: Defines a minority FTLD–FUS class (overview) (clayton2024synaptopathypresynapticconvergence pages 1-2, huber2024mechanismsofneurodegeneration pages 57-60). - TMEM106B: Genetic modifier in FTLD–TDP; risk alleles/filament accumulation associate with endolysosomal defects, impaired RNA transport/local translation, and heightened TDP-43 dysfunction; knockdown increases DPR accumulation and disrupts autophagosome–lysosome maturation (mechanistic synthesis) (huber2024mechanismsofneurodegeneration pages 57-60, huber2024mechanismsofneurodegenerationb pages 57-60, huber2024mechanismsofneurodegenerationa pages 57-60). - UNC13A: Presynaptic vesicle priming factor; TDP-43–dependent cryptic exon inclusion and poly-PR decrease UNC13A, linking TDP-43 pathology to synaptic failure (huber2024mechanismsofneurodegeneration pages 57-60, huber2024mechanismsofneurodegenerationb pages 57-60).

  • Chemical entities (CHEBI terms; selected)
  • Glucosylsphingosine (GlcSph), ganglioside GM2, globoside GB3: Lysosomal lipid biomarkers increased in brain regions affected by GRN and sporadic FTD; plasma GlcSph elevated in asymptomatic GRN carriers (https://doi.org/10.1101/2024.02.09.579529, Feb 2024) (hsiaonakamoto2024alterationsinlysosomal pages 1-5, hsiaonakamoto2024alterationsinlysosomal pages 30-33).
  • Neurofilament light (NfL): Axonal injury biomarker elevated across genetic and sporadic FTD; correlates with clinical severity and progression (https://doi.org/10.1101/2024.02.09.579529, Feb 2024) (hsiaonakamoto2024alterationsinlysosomal pages 1-5, huber2024mechanismsofneurodegenerationa pages 79-82).
  • GFAP (astroglial), YKL-40 (CHI3L1): Glial biomarkers elevated in asymptomatic GRN carriers and symptomatic FTD groups (pattern varies by genotype); tissue YKL-40 increased in affected regions (https://doi.org/10.1101/2024.02.09.579529, 2024) (hsiaonakamoto2024alterationsinlysosomal pages 1-5, hsiaonakamoto2024alterationsinlysosomal pages 30-33).

  • Synaptic proteins NPTX2, NPTXR (neuronal pentraxins), VGF: Reduced in CSF across FTD, most pronounced in MAPT carriers; some correlate with disease severity (https://doi.org/10.1101/2024.02.09.579529, 2024) (hsiaonakamoto2024alterationsinlysosomal pages 1-5, hsiaonakamoto2024alterationsinlysosomal pages 30-33).

  • Cell Types (CL terms; selected)

  • Neurons (principal cortical pyramidal neurons): primary degenerating cells with early synaptic failure (clayton2024synaptopathypresynapticconvergence pages 1-2).
  • Microglia: show disease-associated activation; in GRN deficiency, cell-intrinsic TDP-43 aggregation and lysosomal defects with complement activation; glial biomarkers elevated (sung2024progranulinhaploinsufficiencymediates pages 1-2, hsiaonakamoto2024alterationsinlysosomal pages 1-5).
  • Astrocytes: reactive in FTLD; GFAP elevated in plasma/CSF; contribute to neuroinflammation and synaptic environment (hsiaonakamoto2024alterationsinlysosomal pages 1-5, hsiaonakamoto2024alterationsinlysosomal pages 30-33).

  • Oligodendrocytes: can harbor inclusions in FTLD–TDP subtypes (overview) (huber2024mechanismsofneurodegeneration pages 57-60).

  • Anatomical locations (UBERON terms; selected)

  • Frontal and temporal cortices with prominent involvement of paralimbic fronto–insular–striatal (salience-related) networks; selective vulnerability of anterior temporal and insular regions underlies bvFTD and language variants (https://doi.org/10.15496/publikation-94419, May 2024) (reinermann2024thefunctionalconnectivity pages 14-17).

3) Biological Processes (for GO annotation; selected disrupted processes) - Protein aggregation, phase separation and inclusion formation (TDP-43, tau, FUS) (huber2024mechanismsofneurodegeneration pages 57-60, clayton2024synaptopathypresynapticconvergence pages 1-2). - RNA splicing/processing and RNA transport (TDP-43 loss-of-function; global RNA splicing module increases in CSF proteomics) (saloner2025largescalenetworkanalysis pages 1-7, huber2024mechanismsofneurodegeneration pages 57-60). - Nucleocytoplasmic transport (impaired in C9orf72 expansion disease) (saloner2025largescalenetworkanalysis pages 1-7). - Autophagy and lysosome organization/acidification; cargo trafficking (GRN/TMEM106B axis) (sung2024progranulinhaploinsufficiencymediates pages 1-2, huber2024mechanismsofneurodegeneration pages 57-60). - Synaptic vesicle priming/exocytosis and presynaptic homeostasis (UNC13A, vesicle cycle) (clayton2024synaptopathypresynapticconvergence pages 1-2, huber2024mechanismsofneurodegeneration pages 57-60). - Complement activation and innate immune signaling in glia (C1q, YKL-40 elevation; microglial activation) (sung2024progranulinhaploinsufficiencymediates pages 1-2, hsiaonakamoto2024alterationsinlysosomal pages 1-5, hsiaonakamoto2024alterationsinlysosomal pages 30-33). - Extracellular matrix remodeling (MAPT-associated CSF modules) (saloner2025largescalenetworkanalysis pages 1-7).

4) Cellular Components (selected) - Presynapse/synaptic vesicle pool; active zone (UNC13A-dependent priming) (clayton2024synaptopathypresynapticconvergence pages 1-2, huber2024mechanismsofneurodegeneration pages 57-60). - Lysosomes, late endosomes, autophagosomes and autolysosomes (GRN/TMEM106B-dependent maturation and acidification) (sung2024progranulinhaploinsufficiencymediates pages 1-2, huber2024mechanismsofneurodegeneration pages 57-60). - Stress granules and ribonucleoprotein assemblies (RNA-binding proteinopathies; overview) (huber2024mechanismsofneurodegeneration pages 57-60). - Nucleus and cytoplasm (TDP-43 nucleocytoplasmic mislocalization) (huber2024mechanismsofneurodegeneration pages 57-60, saloner2025largescalenetworkanalysis pages 1-7).

5) Disease Progression - Sequence of events (typical mechanistic cascade): genetic risk/trigger (e.g., C9orf72 expansion; GRN loss; MAPT mutation; TMEM106B risk) → proteinopathy (TDP-43/tau/FUS misfolding and mislocalization) → early presynaptic dysfunction (vesicle priming/turnover; local translation) → impaired autophagy–lysosome clearance and nucleocytoplasmic transport → reactive glial responses and complement signaling → progressive neuronal/synaptic loss and network disintegration in frontal/temporal systems, manifesting as bvFTD or PPA variants (synthesis from reviews and biomarker/proteomics data) (clayton2024synaptopathypresynapticconvergence pages 1-2, huber2024mechanismsofneurodegeneration pages 57-60, saloner2025largescalenetworkanalysis pages 1-7, hsiaonakamoto2024alterationsinlysosomal pages 1-5). - Subtypes/stages: FTLD–TDP subtyping (A–D) and mixed pathologies occur; autosomal-dominant FTLD shows genotype-associated CSF module shifts (e.g., RNA splicing↑ in GRN/C9; ECM↑ in MAPT) and synaptic/autophagy module↓; these shifts mirror progression toward synaptic failure and lysosomal compromise (https://doi.org/10.21203/rs.3.rs-4103685/v1, 2025) (saloner2025largescalenetworkanalysis pages 1-7, hsiaonakamoto2024alterationsinlysosomal pages 1-5).

6) Phenotypic Manifestations - Core clinical phenotypes: behavioral variant FTD (bvFTD: disinhibition, apathy, loss of empathy, compulsions), and primary progressive aphasia variants (semantic and non-fluent/agrammatic), reflecting selective degeneration of salience/semantic networks in frontal/anterior temporal systems (network-level account) (https://doi.org/10.15496/publikation-94419, 2024) (reinermann2024thefunctionalconnectivity pages 14-17). - Clinicopathological links and mechanisms: presynaptic synaptopathy correlates with early cognitive/behavioral dysfunction; TDP-43 loss-of-function impacts synaptic genes (UNC13A), while GRN and TMEM106B lysosome biology contributes to neuroinflammation and clearance failure; in MAPT, synaptic/ECM alterations are prominent (synthesis) (clayton2024synaptopathypresynapticconvergence pages 1-2, huber2024mechanismsofneurodegeneration pages 57-60, saloner2025largescalenetworkanalysis pages 1-7, hsiaonakamoto2024alterationsinlysosomal pages 1-5).

Gene/protein annotations with ontology terms (examples) - GRN (HGNC:4601): lysosomal protein; processes: lysosome organization, regulation of inflammatory response, autophagy; components: lysosome, late endosome; evidence: human microglia TDP-43 aggregation with lysosomal abnormalities, complement activation in GRN haploinsufficiency (https://doi.org/10.1186/s12974-024-03039-1, 2024) (sung2024progranulinhaploinsufficiencymediates pages 1-2). - C9orf72 (HGNC:28339): GTPase regulator/trafficking; processes: nucleocytoplasmic transport, RNA metabolism, proteostasis; components: nucleus, cytoplasm, nuclear pore; evidence: combined loss- and gain-of-function with TDP-43 aggregation (https://doi.org/10.21203/rs.3.rs-4103685/v1, 2025) (saloner2025largescalenetworkanalysis pages 1-7). - MAPT (HGNC:6893): microtubule-associated protein; processes: microtubule stabilization, synaptic signaling; components: axon, somatodendritic compartments; evidence: ECM↑ and synaptic signaling alterations in MAPT FTLD CSF networks (https://doi.org/10.21203/rs.3.rs-4103685/v1, 2025) (saloner2025largescalenetworkanalysis pages 1-7). - TARDBP/TDP-43 (HGNC:11577): RNA-binding protein; processes: RNA splicing/transport; components: nucleus, cytoplasm; evidence: presynaptic synaptopathy via UNC13A dysregulation (review) (huber2024mechanismsofneurodegeneration pages 57-60, clayton2024synaptopathypresynapticconvergence pages 1-2). - FUS (HGNC:4010): RNA-binding; processes: RNA metabolism, stress granules; components: nucleus, stress granules; evidence: minority FTLD–FUS class (overview) (huber2024mechanismsofneurodegeneration pages 57-60, clayton2024synaptopathypresynapticconvergence pages 1-2). - TMEM106B (HGNC:24797): lysosomal membrane protein; processes: autophagosome–lysosome fusion, lysosomal acidification; components: lysosome, endolysosomal system; evidence: genetic modifier; DPR clearance; endolysosomal disruption (huber2024mechanismsofneurodegeneration pages 57-60, huber2024mechanismsofneurodegenerationb pages 57-60). - UNC13A (HGNC:12535): presynaptic priming; processes: synaptic vesicle exocytosis; components: active zone; evidence: TDP-43–dependent vulnerability and synaptic dysfunction (huber2024mechanismsofneurodegeneration pages 57-60, huber2024mechanismsofneurodegenerationb pages 57-60).

Phenotype associations (examples; HP terms) - Behavioral disinhibition, apathy, loss of empathy, compulsive behaviors, executive dysfunction; expressive language deficits (semantic variant, non-fluent variant) (network/clinical synthesis) (reinermann2024thefunctionalconnectivity pages 14-17).

Cell type involvement (examples; CL terms) - Neuron (principal excitatory neuron), microglial cell, astrocyte, oligodendrocyte; endothelial/vascular involvement is under active study but not established by the evidence set cited here (clayton2024synaptopathypresynapticconvergence pages 1-2, sung2024progranulinhaploinsufficiencymediates pages 1-2, hsiaonakamoto2024alterationsinlysosomal pages 1-5).

Anatomical locations (UBERON terms) - Frontal lobe, temporal lobe, insula, anterior temporal pole; paralimbic fronto–insular–striatal network elements (reinermann2024thefunctionalconnectivity pages 14-17).

Chemical entities (CHEBI terms) - Glucosylsphingosine (GlcSph), ganglioside GM2, globoside GB3; NfL (protein biomarker), GFAP, YKL-40; neuronal pentraxins (NPTX2/NPTXR); VGF (hsiaonakamoto2024alterationsinlysosomal pages 1-5, hsiaonakamoto2024alterationsinlysosomal pages 30-33, huber2024mechanismsofneurodegenerationa pages 79-82).

Evidence items and key statistics - Pathological classes and convergence: Most FTD belongs to FTLD–TDP or FTLD–tau; FTLD–FUS is less common. Early presynaptic dysfunction is a convergent, likely initiating mechanism across genetic backgrounds (https://doi.org/10.1093/brain/awae074, 2024) (clayton2024synaptopathypresynapticconvergence pages 1-2, huber2024mechanismsofneurodegeneration pages 57-60). - TMEM106B modifies FTLD–TDP: risk alleles/filaments link to TDP-43 dysfunction and endolysosomal impairment; knockdown increases C9 DPRs and blocks autophagosome–lysosome maturation (mechanistic evidence compiled) (huber2024mechanismsofneurodegeneration pages 57-60, huber2024mechanismsofneurodegenerationb pages 57-60, huber2024mechanismsofneurodegenerationa pages 57-60). - GRN haploinsufficiency: human microglia from GRN-FTD show cytoplasmic TDP-43 aggregation, lysosomal abnormalities, complement C1q activation, and impaired phagocytosis (https://doi.org/10.1186/s12974-024-03039-1, Feb 2024) (sung2024progranulinhaploinsufficiencymediates pages 1-2). - CSF proteomics in genetic FTLD (n≈116 carriers vs 39 controls): RNA-splicing modules↑ (C9orf72, GRN), ECM modules↑ (MAPT), synaptic/neuronal and autophagy modules↓; signatures generalize to independent cohorts (https://doi.org/10.21203/rs.3.rs-4103685/v1, Mar 2025) (saloner2025largescalenetworkanalysis pages 1-7). - Biofluid/tissue biomarkers across FTD: plasma/CSF NfL↑ across forms (severity correlation); plasma GFAP↑ and CSF YKL-40↑ (notably in GRN and MAPT); CSF NPTX2/NPTXR↓ and VGF↓ (synaptic loss), strongest in MAPT; lysosomal lipids (GlcSph, GM2, GB3)↑ in disease-affected cortex; some markers (e.g., NPTXR) correlate with CDR+NACC FTLD severity (https://doi.org/10.1101/2024.02.09.579529, Feb 2024) (hsiaonakamoto2024alterationsinlysosomal pages 1-5, hsiaonakamoto2024alterationsinlysosomal pages 30-33, hsiaonakamoto2024alterationsinlysosomal pages 33-38).

Applications and real‑world implementations - Biomarker applications: NfL (plasma/CSF) as a prognostic and pharmacodynamic marker across FTLD; plasma GFAP and CSF YKL‑40 for glial activation; CSF neuronal pentraxins (NPTX2/NPTXR) for synaptic integrity; genotype‑specific lysosomal lipids (e.g., plasma GlcSph in GRN) for stratification and presymptomatic monitoring; AD biomarkers (Aβ42/40, p‑tau) to exclude AD copathology in differential diagnosis (https://doi.org/10.1101/2024.02.09.579529, 2024; biomarker review perspective) (hsiaonakamoto2024alterationsinlysosomal pages 1-5, huber2024mechanismsofneurodegenerationa pages 79-82). - Therapeutic directions informed by mechanisms: Targeting lysosomal biology (GRN replacement/augmentation; TMEM106B modulation), nucleocytoplasmic transport (C9orf72 pathways), and synaptic resilience (UNC13A/synaptic vesicle cycle) are rational avenues suggested by convergent mechanisms and CSF network signatures (https://doi.org/10.21203/rs.3.rs-4103685/v1, 2025; mechanistic syntheses) (saloner2025largescalenetworkanalysis pages 1-7, huber2024mechanismsofneurodegeneration pages 57-60, clayton2024synaptopathypresynapticconvergence pages 1-2).

Expert opinions and analysis from authoritative sources - A 2024 Brain review synthesizes convergent presynaptic synaptopathy across ALS–FTD, arguing it is an early and targetable hub across genetic backgrounds (https://doi.org/10.1093/brain/awae074, Mar 2024) (clayton2024synaptopathypresynapticconvergence pages 1-2). - Mechanistic syntheses emphasize TMEM106B and UNC13A as central modulators linking lysosomal/autophagy and presynaptic machinery to TDP‑43 pathology, recommending pathway‑focused biomarker development (huber2024mechanismsofneurodegeneration pages 57-60, huber2024mechanismsofneurodegenerationb pages 57-60). - Systems proteomics in genetic FTLD recommends network‑based biomarker panels and highlights RNA splicing, ECM, synaptic, and autophagy modules as translational anchors (https://doi.org/10.21203/rs.3.rs-4103685/v1, 2025) (saloner2025largescalenetworkanalysis pages 1-7).

Ontology‑ready annotations (examples) - Genes/Proteins (HGNC): GRN; C9orf72; MAPT; TARDBP; FUS; TMEM106B; UNC13A (sung2024progranulinhaploinsufficiencymediates pages 1-2, saloner2025largescalenetworkanalysis pages 1-7, huber2024mechanismsofneurodegeneration pages 57-60). - GO Biological Process: protein aggregation; RNA splicing; nucleocytoplasmic transport; autophagy; lysosome organization; synaptic vesicle exocytosis; microglial activation; complement activation (saloner2025largescalenetworkanalysis pages 1-7, huber2024mechanismsofneurodegeneration pages 57-60, sung2024progranulinhaploinsufficiencymediates pages 1-2, hsiaonakamoto2024alterationsinlysosomal pages 1-5). - GO Cellular Component: presynapse; synaptic vesicle; lysosome; autophagosome; nucleus; cytoplasm (clayton2024synaptopathypresynapticconvergence pages 1-2, huber2024mechanismsofneurodegeneration pages 57-60, sung2024progranulinhaploinsufficiencymediates pages 1-2). - Cell Types (CL): neuron; microglial cell; astrocyte; oligodendrocyte (clayton2024synaptopathypresynapticconvergence pages 1-2, sung2024progranulinhaploinsufficiencymediates pages 1-2, hsiaonakamoto2024alterationsinlysosomal pages 1-5, huber2024mechanismsofneurodegeneration pages 57-60). - Anatomical (UBERON): frontal lobe; temporal lobe; insula; anterior temporal pole (reinermann2024thefunctionalconnectivity pages 14-17). - Chemicals (CHEBI): glucosylsphingosine; ganglioside GM2; globoside GB3; neurofilament light; GFAP; YKL‑40; NPTX2; NPTXR; VGF (hsiaonakamoto2024alterationsinlysosomal pages 1-5, hsiaonakamoto2024alterationsinlysosomal pages 30-33, huber2024mechanismsofneurodegenerationa pages 79-82).

Notes on prevalence/incidence - Epidemiology varies by study/region; mechanistic reviews emphasize FTD as a leading cause of young‑onset dementia with high heritability and frequent autosomal‑dominant forms (network/overview context) (huber2024mechanismsofneurodegenerationa pages 33-38, reinermann2024thefunctionalconnectivity pages 14-17). Because robust, region‑specific incidence statistics were not directly available in the evidence set cited here, summary rates are not included; readers should refer to contemporary epidemiologic consortia for region‑specific denominators.

Cited sources (URLs and publication dates embedded above; ID mapping for statements) - Presynaptic convergence in ALS–FTD: Brain (Mar 2024): https://doi.org/10.1093/brain/awae074 (clayton2024synaptopathypresynapticconvergence pages 1-2). - Mechanism-focused syntheses with TMEM106B/UNC13A, FTLD class overview: 2024 synaptic–mechanism review (huber2024mechanismsofneurodegeneration pages 57-60, huber2024mechanismsofneurodegenerationb pages 57-60, huber2024mechanismsofneurodegenerationa pages 57-60). - GRN microglia TDP-43 aggregation and lysosomal abnormalities: J Neuroinflammation (Feb 2024): https://doi.org/10.1186/s12974-024-03039-1 (sung2024progranulinhaploinsufficiencymediates pages 1-2). - Systems CSF proteomics in genetic FTLD: Research Square (Mar 2025): https://doi.org/10.21203/rs.3.rs-4103685/v1 (saloner2025largescalenetworkanalysis pages 1-7). - Biofluid/tissue biomarkers across sporadic and genetic FTD (lysosomal lipids, glial and synaptic markers): bioRxiv (Feb 2024): https://doi.org/10.1101/2024.02.09.579529 (hsiaonakamoto2024alterationsinlysosomal pages 1-5, hsiaonakamoto2024alterationsinlysosomal pages 30-33, hsiaonakamoto2024alterationsinlysosomal pages 33-38). - Network/anatomical locus emphasis: doctoral thesis (May 2024): https://doi.org/10.15496/publikation-94419 (reinermann2024thefunctionalconnectivity pages 14-17).

Direct quotes (selected) - “iMGs from FTD–GRN patients with PGRN deficiency exhibited… cytoplasmic TDP-43 aggregation and… lysosomal abnormalities… mediated by complement C1q activation” (J Neuroinflammation, Feb 2024) (sung2024progranulinhaploinsufficiencymediates pages 1-2). - “This evidence indicates that presynaptic synaptopathy is an early and convergent event in frontotemporal dementia and amyotrophic lateral sclerosis” (Brain, Mar 2024) (clayton2024synaptopathypresynapticconvergence pages 1-2).

Limitations and gaps - Pathology-specific in vivo biomarkers (e.g., direct assays for TDP-43 or DPRs) remain under development; NfL and glial/synaptic markers offer staging and monitoring but are not pathology-specific. Future work should integrate network proteomics, genotype‑specific lipidomics, and synaptic panels to enhance differential diagnosis and target engagement (huber2024mechanismsofneurodegenerationa pages 79-82, saloner2025largescalenetworkanalysis pages 1-7, hsiaonakamoto2024alterationsinlysosomal pages 1-5).

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