AD-PD-FTD Comparison Matrix

AD-PD-FTD Comparison Matrix

Overview

This page provides a comprehensive comparison of Alzheimer's Disease (AD), Parkinson's Disease (PD), and Frontotemporal Dementia (FTD)—three major neurodegenerative disorders with overlapping but distinct clinical and pathological features. Understanding their similarities and differences is essential for accurate diagnosis, prognostic counseling, and therapeutic development[@iza2019].

Comparison Table

| Feature | Alzheimer's Disease | Parkinson's Disease | Frontotemporal Dementia |
|---------|-------------------|-------------------|------------------------|
| Onset Age | Typically >65 years | Typically >60 years | Typically 45-65 years |
| Prevalence | ~6 million (US) | ~1 million (US) | ~50,000-60,000 (US) |
| Key Pathology | Amyloid plaques, neurofibrillary tangles | Lewy bodies (α-synuclein) | Tau or TDP-43 inclusions[@neumann2019] |
| Primary Proteins | Aβ, tau | α-synuclein[@spillantini2000] | Tau, TDP-43 |
| Affected Regions | Hippocampus, cortex | Substantia nigra, basal ganglia | Frontal and temporal lobes[@seeley2009] |
| Motor Symptoms | Late stage | Early, prominent | Variable |
| Cognitive Symptoms | Memory loss prominent | Executive dysfunction | Language, behavior prominent |
| Memory Loss | Early, prominent | Variable | Usually later |
| Disease Duration | 8-12 years | 15-20 years | 6-11 years |

Epidemiology Comparison

Prevalence and Incidence

AD-PD-FTD Comparison Matrix

Overview

This page provides a comprehensive comparison of Alzheimer's Disease (AD), Parkinson's Disease (PD), and Frontotemporal Dementia (FTD)—three major neurodegenerative disorders with overlapping but distinct clinical and pathological features. Understanding their similarities and differences is essential for accurate diagnosis, prognostic counseling, and therapeutic development[@iza2019].

Comparison Table

| Feature | Alzheimer's Disease | Parkinson's Disease | Frontotemporal Dementia |
|---------|-------------------|-------------------|------------------------|
| Onset Age | Typically >65 years | Typically >60 years | Typically 45-65 years |
| Prevalence | ~6 million (US) | ~1 million (US) | ~50,000-60,000 (US) |
| Key Pathology | Amyloid plaques, neurofibrillary tangles | Lewy bodies (α-synuclein) | Tau or TDP-43 inclusions[@neumann2019] |
| Primary Proteins | Aβ, tau | α-synuclein[@spillantini2000] | Tau, TDP-43 |
| Affected Regions | Hippocampus, cortex | Substantia nigra, basal ganglia | Frontal and temporal lobes[@seeley2009] |
| Motor Symptoms | Late stage | Early, prominent | Variable |
| Cognitive Symptoms | Memory loss prominent | Executive dysfunction | Language, behavior prominent |
| Memory Loss | Early, prominent | Variable | Usually later |
| Disease Duration | 8-12 years | 15-20 years | 6-11 years |

Epidemiology Comparison

Prevalence and Incidence

Alzheimer's Disease:

• Most common cause of dementia (60-80% of cases)
• Prevalence doubles every 5 years after age 65
• ~6.5 million Americans living with AD

• Second most common neurodegenerative disorder
• ~1 million Americans with PD
• 60,000 new diagnoses annually

• Second most common cause of young-onset dementia
• Accounts for 10-20% of all dementias
• Equal distribution between bvFTD and language variants

Risk Factors

| Risk Factor | AD | PD | FTD |
|-------------|-----|-----|-----|
| Age | Primary risk factor | Primary risk factor | Earlier onset |
| Family history | Significant | Significant | Strong (40-50% cases) |
| APOE ε4 | Strong risk | No effect | No effect |
| Head trauma | Possible risk | Possible risk | Possible |
| Education | Lower = higher risk | No clear effect | No clear effect |

Neuropathology

Alzheimer's Disease Pathology

AD is characterized by two hallmark proteinopathies[@beach2018]:

• Diffuse plaques: Early, not strongly correlated with cognition
• Neuritic plaques: Dense core,-correlated with cognitive impairment

• Follow Braak staging (I-VI) from entorhinal cortex to neocortex
• Strong correlation with cognitive impairment

Parkinson's Disease Pathology

PD is defined by[@spillantini2000][@kalia2015]:

• Phosphorylated α-synuclein (pSer129)
• Ubiquitin-positive, spherical, with halo

• Loss of melanized neurons in substantia nigra pars compacta (50-70%)
• Correlation with motor symptoms

Frontotemporal Dementia Pathology

FTD encompasses multiple proteinopathies[@neumann2019]:

• Pick's disease (3R tau)
• CBD (4R tau)
• PSP (4R tau)
• FTDP-17 (3R/4R tau mutations)

• Type A (most common): GRN mutations
• Type B: ALS-associated
• Type C: Semantic variant PPA
• Type D: VCP mutations

• Atypical FTLD with ubiquitin-only pathology

Motor Symptoms Comparison

| Symptom | AD | PD | FTD |
|---------|----|----|-----|
| Tremor | Rare | Early, resting | Rare |
| Bradykinesia | Late | Early, prominent | Rare |
| Rigidity | Late | Early, prominent | Variable |
| Gait disturbance | Late | Early | Variable |
| Falls | Late | Early | Variable |
| Postural instability | Late | Early (H&Y 3+) | Variable |
| Dystonia | Rare | Variable | Variable |
| Myoclonus | Rare (late) | Variable | Variable |

Cognitive Symptoms Comparison

| Domain | AD | PD | FTD |
|--------|----|----|-----|
| Memory | Early, prominent | Working memory | Episodic relatively spared |
| Executive function | Early | Early | Early, prominent |
| Language | Late | Variable | Early, prominent |
| Visuospatial | Early | Variable | Usually spared |
| Behavior | Late | Variable | Early, prominent |
| Social cognition | Late | Variable | Early (bvFTD) |

Genetic Risk Factors

Alzheimer's Disease

| Gene | Variant | Effect | Notes |
|------|---------|--------|-------|
| [APOE](/genes/apoe) | ε4 | Strong risk | Most significant genetic factor |
| [APOE](/genes/apoe) | ε2 | Protective | Reduces risk by ~40% |
| [TREM2](/genes/trem2) | R47H | Moderate risk | Immune receptor, microglial function |
| [APP](/genes/app) | Swedish | Causative | Early-onset familial AD |
| [PSEN1](/genes/psen1) | Multiple | Causative | Early-onset familial AD |
| [PSEN2](/genes/psen2) | Multiple | Causative | Early-onset familial AD |

Parkinson's Disease

| Gene | Effect | Inheritance | Notes |
|------|--------|-------------|-------|
| [LRRK2](/genes/lrrk2) | Moderate risk | Autosomal dominant | Most common genetic cause |
| [GBA](/genes/gba) | Moderate risk | Autosomal recessive | Faster cognitive decline |
| [SNCA](/genes/snca) | Causative | Autosomal dominant | First identified PD gene |
| [PARKIN](/genes/parkin) | Early-onset | Autosomal recessive | Juvenile onset |
| [PINK1](/genes/pink1) | Early-onset | Autosomal recessive | Similar to PARKIN |
| [DJ-1](/genes/dj1) | Early-onset | Autosomal recessive | Rare |

Frontotemporal Dementia

| Gene | Effect | Protein | Notes |
|------|--------|---------|-------|
| [MAPT](/genes/mapt) | Causative/risk | Tau | Intron mutations, P301L |
| [GRN](/genes/grn) | Causative | Progranulin | Haploinsufficiency |
| [C9orf72](/genes/c9orf72) | Causative | Dipeptide repeats | Most common cause |
| [VCP](/genes/vcp) | Causative | Valosin-containing protein | PDBSS syndrome |
| [FUS](/genes/fus) | Rare | FUS protein | ALS-FTD overlap |

Biomarkers

| Biomarker | AD | PD | FTD |
|-----------|----|----|-----|
| Amyloid PET | Positive | Negative | Usually negative |
| Tau PET | Positive (AD pattern) | Variable (Limbic) | Variable (FTD pattern) |
| CSF Aβ42 | Decreased | Normal | Normal |
| CSF total tau | Increased | Normal | Normal (usually) |
| CSF p-tau | Increased | Normal | Normal (usually) |
| α-synuclein RT-QuIC | Negative | Positive (70-90%) | Negative |
| Neurofilament light | Increased (later) | Increased (later) | Increased |
| FDG-PET | Temporoparietal hypometabolism | Posterior cingulate | Frontal hypometabolism |

Advanced Biomarker Techniques

Imaging Biomarkers:

• Amyloid PET (Pittsburgh Compound B, florbetapir)
• Tau PET (flortaucipir, MK-6240)
• FDG-PET for metabolic patterns
• Diffusion tensor imaging for white matter integrity
• PET for neurotransmitter systems (dopamine, serotonin)

• Plasma Aβ42/40 ratio
• Plasma tau (NfL, p-tau181, p-tau217)
• Neurofilament light chain (NfL)
• Alpha-synuclein seed amplification assay

Treatment Approaches

| Approach | AD | PD | FTD |
|----------|----|----|-----|
| Cholinesterase inhibitors | Donepezil, rivastigmine, galantamine | May help (especially with dementia) | Limited benefit |
| NMDA antagonist | Memantine | Not standard | Not standard |
| Dopamine agonists | Not used | Pramipexole, ropinirole | Not used |
| Levodopa | Not used | First-line | Not used |
| Immunotherapy | Lecanemab, donanemab | In development | In development |
| Anti-aggregants | In trials | In trials | In trials |
| Gene therapy | Emerging | Emerging | Emerging |

Disease-Modifying Therapies in Development

Alzheimer's Disease:

• Lecanemab (anti-Aβ protofibrils) — FDA approved
• Donanemab (anti-N-terminal Aβ) — FDA approved
• Remternetug (anti-Aβ bispecific)
• Multiple tau-targeted immunotherapies

• Gene therapies (AAV-GAD, AAV-AADC)
• Alpha-synuclein antibodies (cinpanemab, samulimab)
• LRRK2 inhibitors (DNL151, BIIB122)

• Anti-tau therapies (LMTM, ASP-ADAS)
• Anti-TDP-43 therapies (emerging)
• Progranulin replacement therapies

Disease Progression

Alzheimer's Disease Progression

| Stage | Duration | Features |
|-------|----------|----------|
| Preclinical | Years to decades | Biomarkers positive, no symptoms |
| MCI due to AD | 2-5 years | Objective deficits, preserved function |
| Mild dementia | 2-4 years | Memory loss, instrumental ADLs affected |
| Moderate dementia | 2-6 years | Basic ADLs require assistance |
| Severe dementia | 1-3 years | Complete dependency |

Parkinson's Disease Progression

| Stage | Duration | Features |
|-------|----------|----------|
| Prodromal | Years to decades | RBD, hyposmia, depression |
| Early (H&Y 1-2) | 3-5 years | Motor symptoms, good levodopa response |
| Mid (H&Y 2.5-3) | 5-10 years | Motor fluctuations, dyskinesias |
| Advanced (H&Y 4) | 10-15 years | Disability, falls |
| End-stage (H&Y 5) | 15-20 years | Wheelchair, severe disability |

Frontotemporal Dementia Progression

| Stage | Duration | Features |
|-------|----------|----------|
| Early | 0-3 years | Focal symptoms, preserved function |
| Middle | 3-6 years | Behavioral/cognitive changes |
| Late | 6-10 years | Severe impairment, nursing home |
| End-stage | 8-15 years | Complete dependency |

Cross-References

• [Alzheimer's Disease](/diseases/alzheimers-disease)
• [Parkinson's Disease](/diseases/parkinsons-disease)
• [Frontotemporal Dementia](/diseases/frontotemporal-dementia)
• [Neurodegeneration Comparison Pages](/mechanisms/synaptic-dysfunction-comparison)
• [Disease Progression & Staging](/diseases/disease-progression)

External Links

• [Alzheimer's Association](https://www.alz.org/)
• [Parkinson's Foundation](https://www.parkinson.org/)
• [The Frontotemporal Dementia Research Groups](https://www.ftdrg.org/)
• [PubMed: Dementia Comparison](https://pubmed.ncbi.nlm.nih.gov/?term=dementia+comparison+AD+PD+FTD)