# Frontotemporal lobar degeneration
**Frontotemporal lobar degeneration** (FTLD) is a family of neurodegenerative brain diseases characterized by progressive, relatively localized atrophy of the frontal and temporal lobes, underlying a spectrum of dementias known as frontotemporal dementia (FTD).[5](https://www.ninds.nih.gov/health-information/disorders/dementias) • [2](https://www.ninds.nih.gov/current-research/focus-disorders/alzheimers-disease-and-related-dementias/focus-frontotemporal-dementia-ftd) The term FTLD names the underlying brain disease, while FTD refers to the clinical syndromes it produces; the two labels are often used interchangeably in the literature.[1](https://www.ninds.nih.gov/health-information/disorders/dementia) • [2](https://www.ninds.nih.gov/current-research/focus-disorders/alzheimers-disease-and-related-dementias/focus-frontotemporal-dementia-ftd) Unlike Alzheimer's disease, which produces widespread shrinkage (atrophy) of brain tissue, FTLD primarily targets the frontal lobes, which support reasoning, decision-making, appropriate behavior, and movement, and the temporal lobes, which support memory, word comprehension, object recognition, and emotional responses.[5](https://www.ninds.nih.gov/health-information/disorders/dementias)
| Key fact | Detail |
|---|---|
| Definition | A group of neurodegenerative diseases with progressive atrophy of the frontal and/or temporal lobes, clinically and pathologically heterogeneous[2](https://www.ninds.nih.gov/current-research/focus-disorders/alzheimers-disease-and-related-dementias/focus-frontotemporal-dementia-ftd) |
| Age impact | FTD is the most common form of dementia in people under age 60; onset often occurs in a person's 50s or 60s[2](https://www.ninds.nih.gov/current-research/focus-disorders/alzheimers-disease-and-related-dementias/focus-frontotemporal-dementia-ftd) |
| Prevalence | Population estimates range from 2.7 per 100,000 (peak 9.4 per 100,000 at ages 60 to 69) in Zuid-Holland, Netherlands, to 15.1 per 100,000 in adults under 65 in Cambridge, UK[3](https://pmc.ncbi.nlm.nih.gov/articles/PMC2916644/) |
| Main proteinopathies | About 85% of patients have inclusions of tau (FTLD-tau) or TDP-43 (FTLD-TDP); smaller groups have FUS, ubiquitin-proteasome, or no detectable inclusions[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC6691066/) |
| Genetics | Positive family history in 39 to 50% of cases; autosomal dominant inheritance in 10 to 23%; most frequent mutated genes are C9orf72 (8.2%), MAPT (5.6%), and GRN (4.1%)[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC6691066/) |
| ALS overlap | Motor neuron disease co-occurs in 12.5 to 15% of FTD patients, and FTD shares genetic causes with ALS[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC6691066/) • [2](https://www.ninds.nih.gov/current-research/focus-disorders/alzheimers-disease-and-related-dementias/focus-frontotemporal-dementia-ftd) |
| Prognosis | People can live with frontotemporal disorders for 2 to 10 years, sometimes longer; no treatment cures or reverses them[5](https://www.ninds.nih.gov/health-information/disorders/dementias) |
## Clinical syndromes
FTLD is used as an umbrella term for clinical variants distinguished by their early and predominant symptoms.[3](https://pmc.ncbi.nlm.nih.gov/articles/PMC2916644/) **Behavioral variant FTD** (bvFTD) usually does not affect memory early on but causes changes in behavior, judgment, and personality; affected people may seem uninterested or less caring than their usual selves, and their behavior can seem inappropriate and is sometimes mistaken for a mental health condition.[1](https://www.ninds.nih.gov/health-information/disorders/dementia) Core features of the consensus criteria include behavioral disinhibition, apathy or inertia, [compulsive behavior](https://www.edgepedia.org/compulsive-behavior), dietary changes, and executive dysfunction with spared memory and visuospatial functions.[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC6691066/)
**Language variants** fall under primary progressive aphasia (PPA). Semantic variant PPA presents with impaired comprehension but spared speech production; nonfluent or agrammatic PPA shows agrammatisms and speech apraxia, with effortful speech production, phonologic and grammatical errors, and word retrieval difficulties; logopenic PPA features impaired single-word retrieval (anomia) and impaired sentence or phrase repetition, with single-word comprehension usually spared.[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC6691066/) • [6](https://baycrest.echoontario.ca/wp-content/uploads/2019/02/Frontotemporal-lobar-degeneration-a-consensus-on-clinical-diagnostic-criteria.pdf) • [15](https://pmc.ncbi.nlm.nih.gov/articles/PMC3059138/) Logopenic PPA is only very rarely associated with FTLD; it is more commonly (77%) seen with underlying Alzheimer's pathology.[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC6691066/)
**Motor presentations** include corticobasal syndrome and progressive supranuclear palsy Richardson syndrome, defined by predominant motor symptoms, and FTD associated with motor neuron disease.[7](https://pmc.ncbi.nlm.nih.gov/articles/PMC11590234/pdf/WNL-2024-102076.pdf) FTLD shows significant clinical and pathologic overlap with the atypical parkinsonian disorders corticobasal degeneration (CBD) and progressive supranuclear palsy (PSP).[3](https://pmc.ncbi.nlm.nih.gov/articles/PMC2916644/)
## Neuropathology
Upon post-mortem examination, FTLD is characterized by protein inclusions in degenerating neurons, and the composition of these inclusions defines the pathological classification.[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC6691066/) The neuropathologic classification is based on identifying the protein that accumulates in neurons and glia: tau, TAR DNA-binding protein 43 (TDP-43), and fused in sarcoma (FUS).[8](https://pubmed.ncbi.nlm.nih.gov/24035575/)
**FTLD-tau** groups the tauopathies, including Pick's disease with its Pick bodies, corticobasal degeneration with astrocytic plaques, and progressive supranuclear palsy with tufted astrocytes and neurofibrillary tangles in subcortical nuclei.[9](https://pmc.ncbi.nlm.nih.gov/articles/PMC3928059/) **FTLD-TDP** is defined by ubiquitin-positive, tau-negative inclusions containing TDP-43, with or without motor neuron disease, and is subdivided into types A through E.[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC6691066/) • [10](https://pmc.ncbi.nlm.nih.gov/articles/PMC10184567/) TDP-43 was recognized as the most frequent histological finding in FTLD, a major component of the inclusions in most sporadic and familial FTLD-U cases.[10](https://pmc.ncbi.nlm.nih.gov/articles/PMC10184567/) In FTLD-TDP, TDP-43 deposits aberrantly within the cytoplasm, nucleus, and neurites of neurons and within glial cells, producing neuronal loss in the superficial layers (mainly II and III) of the frontotemporal cortex.[10](https://pmc.ncbi.nlm.nih.gov/articles/PMC10184567/)
The remaining cases are heterogeneous. Some have FUS inclusions (FTLD-FUS); in 10 to 20% of cases originally classified as FTLD-U (5 to 10% of all FTLD), inclusions stain for neither tau nor TDP-43, and some of these are positive only for ubiquitin and p62 (FTLD-UPS), while a small number show no inclusions at all (FTLD-ni).[9](https://pmc.ncbi.nlm.nih.gov/articles/PMC3928059/) • [4](https://pmc.ncbi.nlm.nih.gov/articles/PMC6691066/)
The classification has a history of renaming. For over a hundred years, neuropathologists could report only an unspecific histopathological pattern in patients with behavioral, language, and cognitive problems; names used included "Pick's disease," "frontal lobe degeneration of non-Alzheimer type," and "dementia lacking distinctive histopathology" (DLDH). Many DLDH cases were reclassified as FTLD-U once ubiquitinated inclusions were detected, and finally as FTLD-TDP when the ubiquitinated protein was identified as TDP-43.[10](https://pmc.ncbi.nlm.nih.gov/articles/PMC10184567/)
## Genetics
Heritability plays a major role in FTD, with a positive family history in 39 to 50% of cases and an autosomal dominant presentation in 10 to 23% of patients.[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC6691066/) The most frequent mutated genes with dominant inheritance are C9orf72 (8.2%), the progranulin gene GRN (4.1%), and the microtubule-associated protein tau gene MAPT (5.6%).[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC6691066/) Less frequent disease genes include FUS, CHMP2B, TARDBP, TBK1, VCP, and SQSTM1.[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC6691066/) Heterozygous GRN mutations are a major cause of FTD with neuronal cytoplasmic TDP-43 inclusions.[11](https://arxiv.org/abs/2011.10319)
Correlations exist between causal gene, neuropathology, and clinical presentation, but a one-to-one relationship is lacking.[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC6691066/) Mutation screening of causal genes is indicated when autosomal dominant inheritance is suspected or in early-onset dementia, and may also be offered to at-risk family members.[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC6691066/)
## Epidemiology and course
Population-based prevalence estimates vary with region and age definition: 2.7 per 100,000 overall (peaking at 9.4 per 100,000 in the 60 to 69 age group) in Zuid-Holland, Netherlands, and 15.1 per 100,000 in adults under 65 in Cambridge, UK, where this equals the prevalence of Alzheimer's disease in that population.[3](https://pmc.ncbi.nlm.nih.gov/articles/PMC2916644/) In patients under 65, FTD accounts for approximately 10.2% of all dementias and is the second most common dementia subtype after Alzheimer's disease in this age group.[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC6691066/)
The course varies widely. Some people decline rapidly over two to three years, while others show only minimal changes for many years; people can live with frontotemporal disorders for 2 to 10 years, sometimes longer, but the course is difficult to predict.[5](https://www.ninds.nih.gov/health-information/disorders/dementias)
## Diagnosis
Diagnosis of bvFTD and the language variants rests on clinical diagnostic criteria, complemented by brain MRI, FDG-PET or perfusion SPECT scans, and DNA screening for causal mutations.[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC6691066/) The consensus criteria for possible bvFTD have a sensitivity of 85 to 95% and a specificity of 82%; for probable bvFTD, sensitivity is 75 to 85% and specificity 95%.[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC6691066/) Misdiagnosis is common, most often as Alzheimer's disease, and false-positive diagnoses are most frequent in patients with later onset, no family history, and a more apathetic presentation.[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC6691066/)
**Imaging and fluid biomarkers** refine the diagnosis. Structural MRI in FTD typically shows pronounced volume loss in the frontal and anterior temporal lobes with relative sparing of the hippocampi and medial temporal lobes; reported sensitivity and specificity for differentiating FTD from controls are 70 to 94% and 89 to 99%.[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC6691066/) To distinguish FTD from Alzheimer's disease, cerebrospinal fluid amyloid and tau biomarkers are widely used; in a systematic review with HSROC analysis, the p-tau/Aβ42 ratio showed the best diagnostic performance for this discrimination.[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC6691066/) • [12](https://pubmed.ncbi.nlm.nih.gov/27716663/) Blood-based biomarkers are under active study because they avoid lumbar puncture; a 2025 systematic review examined whether neurofilament light chain (NfL) in CSF or blood can help differentiate bvFTD from psychiatric disorders, a frequent source of diagnostic delay.[13](https://pubmed.ncbi.nlm.nih.gov/40928798/)
## Treatment and research outlook
No treatment currently cures or reverses frontotemporal disorders, and no disease-modifying therapy has been approved.[5](https://www.ninds.nih.gov/health-information/disorders/dementias) • [14](https://pubmed.ncbi.nlm.nih.gov/42865756/) A systematic mapping of the 2026 FTLD therapeutic pipeline identified 38 active interventional trials (19 pharmacological and 19 neuromodulation), comprising 7 Phase 1, 11 Phase 2, and 1 Phase 3 study; neuromodulation accounted for half of the pipeline, predominantly targeting language networks in primary progressive aphasia, while disease-targeted approaches focused mainly on progranulin restoration in GRN-FTD and tau-related mechanisms.[14](https://pubmed.ncbi.nlm.nih.gov/42865756/) [Biomarker](https://www.edgepedia.org/biomarker) outcomes were incorporated in 25 trials (65.8%).[14](https://pubmed.ncbi.nlm.nih.gov/42865756/) The marked biological and clinical heterogeneity of FTLD is among the reasons why no disease-modifying therapy has been approved, and current research emphasizes genetically stratified trial designs and biomarker-guided diagnosis.[14](https://pubmed.ncbi.nlm.nih.gov/42865756/)
## References
1. [Dementia, National Institute of Neurological Disorders and Stroke](https://www.ninds.nih.gov/health-information/disorders/dementia)
2. [Focus On Frontotemporal Dementia (FTD), NINDS](https://www.ninds.nih.gov/current-research/focus-disorders/alzheimers-disease-and-related-dementias/focus-frontotemporal-dementia-ftd)
3. [Frontotemporal Lobar Degeneration: Epidemiology, Pathophysiology, Diagnosis and Management, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC2916644/)
4. [The Use of Biomarkers and Genetic Screening to Diagnose Frontotemporal Dementia: Evidence and Clinical Implications, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC6691066/)
5. [Dementias, National Institute of Neurological Disorders and Stroke](https://www.ninds.nih.gov/health-information/disorders/dementias)
6. [Frontotemporal lobar degeneration: a consensus on clinical diagnostic criteria (Neary et al., 1998)](https://baycrest.echoontario.ca/wp-content/uploads/2019/02/Frontotemporal-lobar-degeneration-a-consensus-on-clinical-diagnostic-criteria.pdf)
7. [Clinical and biomarker study using FTLDNI and 4RTNI data, Neurology (PMC PDF)](https://pmc.ncbi.nlm.nih.gov/articles/PMC11590234/pdf/WNL-2024-102076.pdf)
8. [Frontotemporal lobar degeneration: diversity of FTLD lesions, PubMed](https://pubmed.ncbi.nlm.nih.gov/24035575/)
9. [Frontotemporal lobar degeneration: current perspectives, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC3928059/)
10. [Frontotemporal lobar degeneration with TDP-43: its journey of more than 100 years, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC10184567/)
11. [Homozygous GRN mutations: unexpected phenotypes and new insights, arXiv](https://arxiv.org/abs/2011.10319)
12. [Cerebrospinal Fluid Biomarkers for the Differential Diagnosis between Alzheimer's Disease and Frontotemporal Lobar Degeneration, PubMed](https://pubmed.ncbi.nlm.nih.gov/27716663/)
13. [Neurofilament Light Chain and Differentiation of bvFTD From Psychiatric Disorders: A Systematic Review, PubMed](https://pubmed.ncbi.nlm.nih.gov/40928798/)
14. [Frontotemporal lobar degeneration therapeutic development pipeline: 2026, PubMed](https://pubmed.ncbi.nlm.nih.gov/42865756/)
15. [pmc.ncbi.nlm.nih.gov](https://pmc.ncbi.nlm.nih.gov/articles/PMC3059138/)
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*Topic: Encyclopedia › Life and health › Human health and medicine › Mental health › Dementia & neurocognitive disorders › Frontotemporal disorders*
*Initially written Sep 17, 2026 · Reviewed: Sep 17, 2026; Sep 30, 2026; Oct 21, 2026 · Edited: Sep 30, 2026; Oct 21, 2026 · Last review: Oct 21, 2026*
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License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license