MedGen

In general, frontotemporal dementia (FTD) refers to a clinical manifestation of the pathologic finding of frontotemporal lobar degeneration (FTLD). FTD, the most common subtype of FTLD, is a behavioral variant characterized by changes in social and personal conduct with loss of volition, executive dysfunction, loss of abstract thought, and decreased speech output. A second clinical subtype of FTLD is 'semantic dementia,' characterized by specific loss of comprehension of language and impaired facial and object recognition. A third clinical subtype of FTLD is 'primary progressive aphasia' (PPA), characterized by a reduction in speech production, speech errors, and word retrieval difficulties resulting in mutism and an inability to communicate. All subtypes have relative preservation of memory, at least in the early stages. FTLD is often associated with parkinsonism or motor neuron disease (MND) resembling amyotrophic lateral sclerosis (ALS; 105400) (reviews by Tolnay and Probst, 2002 and Mackenzie and Rademakers, 2007). Mackenzie et al. (2009, 2010) provided a classification of FTLD subtypes according to the neuropathologic findings (see PATHOGENESIS below). Clinical Variability of Tauopathies Tauopathies comprise a clinically variable group of neurodegenerative diseases characterized neuropathologically by accumulation of abnormal MAPT-positive inclusions in nerve and/or glial cells. In addition to frontotemporal dementia, semantic dementia, and PPA, different clinical syndromes with overlapping features have been described, leading to confusion in the terminology (Tolnay and Probst, 2002). Other terms used historically include parkinsonism and dementia with pallidopontonigral degeneration (PPND) (Wszolek et al., 1992); disinhibition-dementia-parkinsonism-amyotrophy complex (DDPAC) (Lynch et al., 1994); frontotemporal dementia with parkinsonism (FLDEM) (Yamaoka et al., 1996); and multiple system tauopathy with presenile dementia (MSTD) (Spillantini et al., 1997). These disorders are characterized by variable degrees of frontal lobe dementia, parkinsonism, motor neuron disease, and amyotrophy. Other neurodegenerative disorders associated with mutations in the MAPT gene include Pick disease (172700) and progressive supranuclear palsy (PSP; 601104). Inherited neurodegenerative tauopathies linked to chromosome 17 and caused by mutation in the MAPT gene have also collectively been termed 'FTDP17' (Lee et al., 2001). Kertesz (2003) suggested the term 'Pick complex' to represent the overlapping syndromes of FTD, primary progressive aphasia (PPA), corticobasal degeneration (CBD), PSP, and FTD with motor neuron disease. He noted that frontotemporal dementia may also be referred to as 'clinical Pick disease' and that the term 'Pick disease' should be restricted to the pathologic finding of Pick bodies. Genetic Heterogeneity of Frontotemporal Lobar Degeneration Mutations in several different genes can cause frontotemporal dementia and frontotemporal lobar degeneration, with or without motor neuron disease. See FTD2 (607485), caused by mutation in the GRN gene (138945) on chromosome 17q21; FTDALS7 (600795), caused by mutation in the CHMP2B gene (609512) on chromosome 3p11; inclusion body myopathy with Paget disease and FTD (IBMPFD; 167320), caused by mutation in the VCP gene (601023) on chromosome 9p13; ALS6 (608030), caused by mutation in the FUS gene (137070) on 16p11; ALS10 (612069), caused by mutation in the TARDBP gene (605078) on 1p36; and FTDALS1 (105550), caused by mutation in the C9ORF72 gene (614260) on 9p21. In 1 family with FTD, a mutation was identified in the presenilin-1 gene (PSEN1; 104311) on chromosome 14, which is usually associated with a familial form of early-onset Alzheimer disease (AD3; 607822). [from OMIM]

Frontotemporal dementia and/or amyotrophic lateral sclerosis-6 (FTDALS6) is an autosomal dominant neurodegenerative disorder with highly variable manifestations. Some patients present in adulthood with progressive FTD, often classified as the 'behavioral variant,' which is characterized by reduced empathy, impulsive behavior, personality changes, and reduced verbal output. Other patients present with features of amyotrophic lateral sclerosis (ALS), which is a fatal neurodegenerative disease characterized by upper and lower motor neuron dysfunction resulting in rapidly progressive paralysis and death from respiratory failure. The pathologic hallmarks of this disease include pallor of the corticospinal tract due to loss of motor neurons (in ALS). In both ALS and FTD, there are ubiquitin-positive inclusions within surviving neurons as well as deposition of pathologic TDP43 (TARDBP; 605078) or p62 (SQSTM1; 601530) aggregates. Patients with a D395G mutation (601023.0014) have been shown to develop pathologic tau (MAPT; 157140) aggregates. Some patients with the disorder may have features of both diseases, and there is significant interfamilial and intrafamilial phenotypic variability (summary by Johnson et al., 2010; Wong et al., 2018; Al-Obeidi et al., 2018; Darwich et al., 2020). For a general phenotypic description and a discussion of genetic heterogeneity of FTDALS, see FTDALS1 (105550). [from OMIM]

Pathological protein aggregates formed by hyperphosphorylation of a microtubule-associated protein known as tau, causing it to aggregate in an insoluble form. [from HPO]

An atypical variant of progressive supranuclear palsy (PSP), a rare late-onset neurodegenerative disease, by prominent early parkinsonism (tremor, limb bradykinesia, axial and limb rigidity) rather than falls and cognitive change. Over the years, patients ultimately develop clinical features characteristic of classical PSP. Neuropathological characteristics includes tau pathology and neuronal loss in specific brain areas, especially in the subthalamic nucleus and substantia nigra. The tau pathology is less severe than in classical PSP. [from ORDO]

Lecanemab is a monoclonal antibody that targets amyloid beta (Aß) aggregates for the treatment of Alzheimer disease (AD). It is approved by the US Food and Drug Administration (FDA) for individuals with mild cognitive impairment (MCI) or mild dementia stage AD with confirmed amyloid pathology. Tests to confirm Aß pathology in the clinical trials included positron emission tomography (PET) or cerebrospinal fluid (CSF) measurement of the Aß42/Total Tau ratio. This disease-modifying medication is based on the amyloid cascade hypothesis, which suggests Aß aggregates are a key driver in AD pathogenesis and that the removal of Aß aggregates should slow cognitive decline. Lecanemab is associated with amyloid-related imaging abnormalities (ARIA) due to edema (ARIA-E) or hemorrhage (ARIA-H) from blood vessels in the brain. Individuals who have one or 2 copies of the AD risk-associated apolipoprotein E (APOE) e4 (NM_000041.4:c.388T>C) allele have an increased risk of ARIA-E or -H. These individuals require additional monitoring during the first year of treatment. The FDA-approved label reports that concomitant antithrombotic medication (aspirin, antiplatelet, or anticoagulant) with lecanemab therapy resulted in intracerebral hemorrhage in 2.5% of individuals during clinical trials.The appropriate use recommendations from the Alzheimer’s Disease and Related Disorders Therapeutics Work Group state that individuals requiring anticoagulants should not be treated with lecanemab until additional data regarding this interaction are available. Both the FDA-approved label and Alzheimer’s Disease and Related Disorders Therapeutics Work group encourage clinicians to consider participation in a registry for AD treatment to gather additional real-world data on lecanemab therapy. [from Medical Genetics Summaries]

A rare late-onset neurodegenerative disease with characteristics of supranuclear gaze palsy, postural instability, progressive rigidity, and mild dementia. Five clinical variants have been described with clinicopathological correlations, with Richardson''s syndrome the most common clinical variant. The disease has neuropathological manifestations of neuronal loss, gliosis with astrocytic plaques and accumulation of tau-immunoreactive neurofibrillary tangles in specific brain areas. The differences in the rate and areas of accumulation of phosphorylated tau protein correlate with the five clinical variants. The disease is a 4R tauopathy composed of a preponderance of four-repeat (exon 10 positive) tau isoforms and a characteristic biochemical profile (doublet tau 64 and tau 69). The MAPT H1-clade specific sub-haplotype, H1c, is a risk factor for this disease. [from SNOMEDCT_US]

Frontotemporal dementia and/or amyotrophic lateral sclerosis-8 (FTDALS8) is an autosomal dominant neurodegenerative disorder characterized by adult-onset dementia manifest as memory impairment, executive dysfunction, and behavioral or personality changes. Some patients may develop ALS or parkinsonism. Neuropathologic studies show frontotemporal lobar degeneration (FTLD) with tau (MAPT; 157140)- and TDP43 (605078)-immunoreactive inclusions (summary by Dobson-Stone et al., 2020). For a discussion of genetic heterogeneity of FTDALS, see FTDALS1 (105550). [from OMIM]

Neurodegenerative disorders involving deposition of abnormal tau protein isoforms (tau proteins) in neurons and glial cells in the brain. Pathological aggregations of tau proteins are associated with mutation of the tau gene on chromosome 17 in patients with alzheimer disease; dementia; parkinsonian disorders; progressive supranuclear palsy (supranuclear palsy, progressive); and corticobasal degeneration. [from MONDO]

An atypical variant of progressive supranuclear palsy (PSP), a rare late-onset neurodegenerative disease, characterized by a variable mixture of progressive asymmetric limb rigidity, apraxia, cortical sensory loss, alien limb, dystonia and bradykinesia that is unresponsive to levodopa. Postural instability and axial rigidity develop as the disease progresses. Neuropathological characteristics includes tau pathology and neuronal loss in specific brain areas, especially in the midfrontal and inferior parietal cortices. [from ORDO]

An atypical variant of progressive supranuclear palsy (PSP), a rare late-onset neurodegenerative disease, characterized by an initial presentation of an isolated speech and language disorder (apraxia of speech, agrammatism, and phonemic errors) years before developing other motor features of PSP. Neuropathological characteristics includes tau pathology and neuronal loss in specific brain areas, especially in the temporal cortex and superior frontal gyrus. [from ORDO]

An atypical variant of progressive supranuclear palsy (PSP), a rare late-onset neurodegenerative disease, characterized by progressive freezing of gait, speech and writing early in the disease course. Later, axial rigidity, and facial immobility can occur, and supranuclear downgaze paresis may emerge after a decade. Neuropathological characteristics include tau pathology and neuronal loss in specific brain areas, especially in the globus pallidus, subthalamic nucleus, and substantia nigra. The tau pathology is less widespread compared to the other PSP sub-types. [from ORDO]

A progressive loss of the ability to remember the meaning of words, faces and objects. [from HPO]