Litvan, Irene

Importance TMEM106B is a frontotemporal lobar degeneration (FTLD) genetic susceptibility factor, and TMEM106B protein aggregates are a feature of aging and neurodegeneration. Whether TMEM106B protein levels are associated with clinical features is unknown. Objective To investigate the clinical associations of cerebrospinal fluid (CSF) TMEM106B in FTLD. Design, Setting, and Participants This cross-sectional study was conducted in 2 independent frontotemporal dementia (FTD) cohorts (recruitment from April 2009 through July 2023, with analyses from January 2025 through April 2026), with a 2-year follow up. This multicenter clinical study integrated clinical, genetic, biomarker, and neuroimaging data. Individuals were recruited through the University of California, San Francisco (n = 3733), or ALLFTD (n = 2343). Participants with available CSF were included. A discovery cohort (n = 271) included participants with sporadic neuropathology-confirmed FTLD; presymptomatic or symptomatic carriers of pathogenic variants in C9orf72 , GRN , or MAPT ; or controls. An independent validation cohort (n = 383) included participants with clinically diagnosed sporadic FTD, Alzheimer disease (AD), and controls. Exposures CSF samples for TMEM106B quantification with aptamer proteomics (SomaScan version 3.0 [discovery cohort] and SomaScan version 4.1 [validation cohort]). Main Outcomes and Measures Parametric tests compared the primary outcome, CSF TMEM106B, by disease severity, TMEM106B rs1990622 genotype, sex, clinical syndrome, pathological diagnosis, and pathogenic variant and determined associations with brain volume. Results In the discovery (n = 271; 136 women [51%]; median [IQR] age, 59 [38-80] years) and validation (n = 383; 183 women [48%]; median [IQR] age, 64 [50-78] years) cohorts, lower CSF TMEM106B was associated with more severe disease (β, −0.15; 95% CI, −0.24 to −0.04; P = .003), lower frontotemporal brain volumes (β, 0.42; 95% CI, 0.24-0.61; P < .001), and faster clinical progression (β, −2.21; 95% CI, −3.70 to −0.72; P = .001). Associations of TMEM106B with clinical disease severity were independent of those with neurofilament light chain. TMEM106B levels were influenced by TMEM106B rs1990622 genotype, where individuals with the protective G/G genotype had lower levels than the risk A/A genotype. CSF TMEM106B levels did not differentiate between FTLD subtypes or between FTLD and AD. Conclusions and Relevance Per the results of this cross-sectional study, TMEM106B is detectable in CSF and levels reflect disease severity in sporadic and genetic FTLD and AD, but levels are also influenced by the TMEM106B rs1990622 genotype. CSF TMEM106B could support further studies to understand the mechanisms of disease and develop clinical tools in FTLD and other neurodegenerative diseases.

Abstract The human X chromosome accounts for ∼5% of the genome. Despite its size, the role of X-chromosomal variants in human diseases is not well understood, mainly due to its distinct inheritance pattern and the frequent omission of sex chromosomes from genome-wide association studies. This study used whole-genome sequencing data from 888 multiple system atrophy (MSA) cases and 7128 controls to perform an X-chromosome-wide common variant association study. Our analyses revealed two sex-differential risk loci: one located at Xq28, associated with increased risk for MSA in females [index variant: rs4898389, odds ratio (OR) = 1.69, 95% confidence interval (CI) = 1.40–2.03, P-value = 2.43 × 10⁻⁸], and another at Xp22.2 within the TBL1X gene, identified in males (index variant: rs6638956, OR = 1.48, 95%CI = 1.26–1.73, P-value = 9.92 × 10⁻⁷). In the Xq28 locus, colocalization analyses pointed to FAM3A and PLXNA3 as genes of interest. These findings emphasize the vital role of sex-differential genetic factors in the pathogenesis of MSA.

Objective Age of symptom onset is highly variable in familial frontotemporal lobar degeneration (f‐FTLD). Accurate prediction of onset would inform clinical management and trial enrollment. Prior studies indicate that individualized maps of brain atrophy can predict conversion to dementia in f‐FTLD. We used a Bayesian linear mixed‐effect (BLME) prediction method for identifying accelerated brain volume loss to predict conversion to dementia. Methods Participants included 234 asymptomatic or prodromal carriers of C9orf72 , GRN , or MAPT mutations (including 21 dementia converters) with ≥3 longitudinal magnetic resonance imaging (MRI) T1‐weighted scans. The BLME models established individual voxel‐wise gray matter trajectories using the first 2 scans. Person‐specific clusters of accelerated volume loss were estimated in subsequent scans and tested as predictors of dementia conversion compared with other approaches in time‐varying Cox proportional hazard models covarying for age. Receiver‐operating characteristic (ROC) curves estimated utility of cluster volume in discriminating which participants converted to dementia within 24 months. Results The BLME cluster volume predicted conversion to dementia in f‐FTLD mutation carriers overall and separately in C9orf72 , GRN , and MAPT , with comparable hazard ratios observed for atrophy W‐maps and regional volumes. Within a 24‐month timeframe, BLME cluster volume discriminated dementia converters from non‐converters with larger areas under the curve (AUCs) than other approaches. Interpretation Bayesian‐modeled individualized atrophy scores predict dementia progression among asymptomatic f‐FTLD mutation carriers and may have increased utility compared with other structural imaging methods when studying individuals over shorter timeframes that align with clinical trial design. ANN NEUROL 20269999:n/a–n/a

Abstract Background Agitation is a clinically significant symptom contributing to behavioral and psychological symptoms of dementia (BPSD) but is poorly understood across the different syndromes related to Frontotemporal Lobar Degeneration (FTLD). This study investigates sex differences in agitation across FTLD‐related syndromes and its relationship to various neuropsychiatric symptoms (NPS). Method We analyzed data from 1,654 participants (916 males, 738 females; average ages 65.8 and 65.9, respectively) from the National Alzheimer's Coordinating Center (NACC) and ARTFL‐LEFFTDS Longitudinal Frontotemporal Lobar Degeneration (ALLFTD) study with a FTLD‐related syndrome: behavioral variant FTD (bvFTD), Primary Progressive Aphasia (non‐fluent variant (nfvPPA), semantic variant (svPPA)), Corticobasal syndrome (CBS) and Progressive Supranuclear Palsy (PSP). Participants’ symptoms were assessed using the Neuropsychiatric Inventory (NPI). Prevalence ratios and odds ratios were computed to assess the likelihood of NPS comorbidities when agitation was present in males and females. Principal Component Analysis (PCA) was performed to identify NPS associated with agitation and how they varied by sex. Result Males were more likely to experience anxiety (bvFTD: p <0.001, CBS: p <0.01, PSP: p <0.0001), apathy (nfvPPA: p <0.01, PSP: p <0.01), depression (bvFTD: p <0.0001, PSP<0.01), disinhibition (nfvPPA: p <0.0001), PSP: p <0.001), and motor symptoms (bvFTD: p <0.01, CBS: p <0.01) when agitation was present. In contrast, females had a higher likelihood of experiencing disinhibition in svPPA ( p <0.001). These findings suggest that agitation is associated with a wider range of NPS in males than in females. Agitation and NPS are especially prominent in males with PSP. Conclusion This study reveals significant sex differences in NPS in FTLD‐related syndromes when agitation is present. Males and especially PSP, are more likely to experience a broader range of NPS in association with agitation. These findings underscore the need for further investigation into the underlying mechanisms driving these sex differences, particularly focusing on the neurobiological impact of agitation, the recognition of symptoms in the presence of greater behavioral disturbances, and potential variations from informant reports. Understanding these factors will provide valuable insights into the role of agitation in the presentation of NPS across FTLD‐related syndromes. Ultimately, addressing these gaps will enhance our ability to effectively treat and manage agitation in both male and female patients with FTLD‐related syndromes.

Abstract Background Staging disease severity in dementia research requires input from an informant. The Clinical Dementia Rating Sum of Boxes (CDR) is the most used instrument for staging in Alzheimer's Disease (AD); but has been expanded to stage patients with frontotemporal lobar degeneration (FTLD) with the CDR PLUS NACC‐FTLD. An informant effect on the CDR has been reported in AD. The aim of this study is to evaluate whether informant characteristics influence the CDR PLUS NACC‐FTLD in a large cohort of participants with frontotemporal dementia (FTD). Method We included participants with a FTLD‐related syndrome from the ALLFTD study. We included participants with a CDR PLUS NACC‐FTLD higher than 0, information on the Montreal Cognitive Assessment (MoCA) scores, and the Neuropsychiatric Inventory Questionnaire (NPI‐Q). We performed a conditional growth model using multilevel linear regression analysis. We performed an exploratory stratified analysis by patient sex. Result We included 1411 participants, totalling 2063 visits. The patient's age at the initial visit was 64.7±9.4 years and 44.0% were females. Females were 69.2% of the informants, and the relationship was 79.1% spouse or partner, 10.6% children, 4.1% were siblings and 6.2% other. The CDR PLUS NACC‐FTLD scores were affected by informant characteristics. The CDR PLUS NACC‐FTLD scores were 0.41 (CI 95%:0.08 to 0.75) higher with female informants. The frequency of visits was associated with a CDR PLUS NACC‐FTLD score 0.86 higher (CI 95%:0.17 to 0.56) when visiting at least once a week, 1.46 higher (CI 95%:0.46 to 2.47) when visiting daily, and 0.83 higher (CI 95%:0.06 to 1.60) when living with the patient compared with visiting less than once a week. As expected, CDR‐FLTD scores increased with lower MoCA and higher NPI‐Q scores. In the stratified analysis by sex, we found that female informant was associated with higher CDR PLUS NACC‐FTLD scores only when patients were male. Conclusion We found that the CDR PLUS NACC‐FTLD is influenced by informant sex and frequency of visits in patients with FTLD‐related syndromes. These results are similar to those observed in AD patients and underscore the need to recognize that informant characteristics may impact dementia severity scales.

ABSTRACT Objective Autosomal dominant progranulin ( GRN ) pathogenic variants are a genetic cause of frontotemporal lobar degeneration. Though clinical trials for GRN ‐related therapies are underway, there is an unmet need for biomarkers that can predict symptom onset and track disease progression. We previously showed that asymptomatic GRN variant carriers exhibit thalamocortical hyperconnectivity that increases with age, presumably as they are approaching symptom onset. Whether hyperconnectivity arises concomitantly with markers of neurodegeneration remains unclear. Methods Utilizing T1 and task‐free functional magnetic resonance imaging from 49 asymptomatic and 26 symptomatic GRN variant carriers, we determined the relationships between functional connectivity, as measured by voxelwise whole‐brain degree, and GRN ‐relevant markers of disease progression, including plasma neurofilament light chain concentrations, cerebrospinal fluid complement C1q and C3b protein levels, obsessive‐compulsive disorder symptom severity, and gray matter volume. Results Neurofilament light chain concentrations were associated with frontotemporoparietal and thalamic hyperconnectivity in asymptomatic GRN variant carriers and extensive regions of atrophy in symptomatic carriers. Complement levels were associated with regions of hyperconnectivity, but not gray matter volume, in symptomatic carriers. Obsessive‐compulsive disorder symptom severity was associated with hypoconnectivity across all GRN carriers. Asymptomatic carriers with thalamic hyperconnectivity tended to have lower gray matter volume in the bilateral insula and left lateral parietal cortex, early regions of atrophy in GRN ‐frontotemporal dementia. Interpretation In asymptomatic carriers, the co‐occurrence of hyperconnectivity, high neurofilament light chain, and low gray matter volume suggests that functional hyperconnectivity may portend the onset of clinical decline. These findings point toward hyperconnectivity as an indicator of approaching symptomatic onset.

Abstract Background Progressive Supranuclear Palsy (PSP) is a rare and severe neurodegenerative tauopathy characterized by diverse clinical phenotypes, including Richardson's syndrome (PSP‐RS), PSP‐parkinsonism (PSP‐P), PSP‐progressive gait freezing (PSP‐PGF), and PSP‐corticobasal syndrome (PSP‐CBS). Significant geographic variation exists in prevalence, clinical presentations, and prognosis. Objectives This global review aims to systematically evaluate the epidemiological variation, clinical phenotypes, diagnostic practices, and management strategies for PSP, focusing on regional disparities and identifying influencing genetic and environmental factors. Methodology A comprehensive literature search following PRISMA guidelines was conducted, analyzing studies reporting PSP epidemiology, phenotypes, diagnostic criteria, risk factors, treatments, and prognoses. Data were categorized into epidemiology, risk factors, clinical presentations, diagnosis, treatment accessibility, and outcomes, considering geographic variation. Results Global PSP prevalence ranges between 5–6.4 per 100,000, influenced by diagnostic criteria and healthcare infrastructure. Clinical manifestations commonly include supranuclear gaze palsy, frequent falls, cognitive impairment, and motor dysfunction. Prognosis significantly varies with subtype; PSP‐RS shows rapid progression and shorter survival (5–7 years), whereas PSP‐P has a milder clinical course (8–12 years). Regional variations highlight differences in genetic predispositions, notably the MAPT H1 haplotype, environmental risk factors such as dietary neurotoxins and industrial pollutants, and accessibility to comprehensive healthcare services. Diagnostic accuracy has improved with the adoption of MDS‐PSP criteria, facilitating recognition of diverse phenotypes. Conclusions Regional disparities in PSP prevalence, phenotypic presentation, and healthcare accessibility underscore the importance of standardized diagnostic criteria, targeted genetic and environmental studies, and equitable healthcare strategies. Enhanced global collaboration is essential for improving PSP diagnosis, management, and patient outcomes worldwide.

Abstract Dementia with Lewy bodies (DLB), a progressive neurodegenerative disease with heterogeneous clinical presentations, greatly impacts patients, caregivers, and society. Despite its frequency, diagnosing and treating DLB remains challenging. Advances in in vivo biomarker assays reflecting underlying pathology are improving disease identification, diagnostic accuracy, and therapeutic development for biologically targeted, disease‐modifying agents. Consequently, definitions of Alzheimer's disease and Parkinson's disease (PD) have shifted to focus on pathological changes occurring before clinical features, with proposed frameworks for detecting pathological amyloid and tau, neurodegeneration, and other markers (National Institute on Aging‐Alzheimer's Association) and alpha‐synucleinopathy and dopaminergic degeneration (Neuronal α‐synuclein Disease Integrated Staging System, SynNeurGe). The biological frameworks, particularly those related to alpha‐synuclein (α‐synuclein), have sparked debate about unifying DLB and PD under a single pathobiologic disease. This paper discusses the implications of these biological frameworks for the DLB community, addressing topics regarding multiple pathologies and neurochemical systems, clinical heterogeneity, and functional impairment, and exploring the potential impact on clinical trials and care. Highlights DLB is a progressive neurodegenerative disease with varied clinical presentations. Diagnosing and treating DLB remains challenging despite its frequency. Biological frameworks are reshaping Alzheimer's and Parkinson's definitions. In vivo biomarkers are improving DLB identification and diagnostic accuracy. Debate exists regarding unifying DLB and Parkinson's under one pathobiology.

AbstractINTRODUCTIONHigher male prevalence in sporadic behavioral variant frontotemporal dementia (bvFTD) has been reported. We hypothesized differences in phenotypes between genetic and sporadic bvFTD females resulting in underdiagnosis of sporadic bvFTD females.METHODSWe included genetic and sporadic bvFTD patients from two multicenter cohorts. We compared behavioral and cognitive symptoms, and gray matter volumes, between genetic and sporadic cases in each sex.RESULTSFemales with sporadic bvFTD showed worse compulsive behavior (p = 0.026) and language impairments (p = 0.024) compared to females with genetic bvFTD (n = 152). Genetic bvFTD females had smaller gray matter volumes than sporadic bvFTD females, particularly in the parietal lobe.DISCUSSIONFemales with sporadic bvFTD exhibit a distinct clinical phenotype compared to females with genetic bvFTD. This difference may explain the discrepancy in prevalence between genetic and sporadic cases, as some females without genetic mutations may be misdiagnosed due to atypical bvFTD symptom presentation.Highlights Sex ratio is equal in genetic behavioral variant of frontotemporal dementia (bvFTD), whereas more males are present in sporadic bvFTD. Distinct neuropsychiatric phenotypes exist between sporadic and genetic bvFTD in females. Phenotype might explain the sex ratio difference between sporadic and genetic cases.