Histopathological changes underlying frontotemporal lobar degeneration with clinicopathological correlation

We have investigated the pathological correlates of dementia in the brains from a consecutive series of 70 patients dying with a clinical diagnosis of frontotemporal lobar degeneration (FTLD). Clinical misdiagnosis rate was low with only 3 patients (4%) failing to show pathological changes consistent with this diagnosis; 1 patient had Alzheimers disease and 2 had cerebrovascular disease (CVD). In the remaining 67 patients, the most common underlying histological cause was ubiquitin pathology with 24 (36%) cases so affected. In these, ubiquitin-positive inclusions were present in the cerebral cortex as small, rounded or crescent-shaped structures within the cytoplasm of neurones of layer II, together with coiled or curvilinear bodies within neurites, and in the hippocampus as small, solid and more spherical-shaped inclusion bodies within the cytoplasm of dentate gyrus granule cells. In one patient, cats eye or lentiform intranuclear ubiquitin inclusions were also present. The second most common histological type was dementia lacking distinctive histology (DLDH), in which neither tau nor ubiquitin inclusions were present, with 16 cases (24%) being affected. Pick-type histology was seen in 14 cases (21%) and tau histological changes associated with frontotemporal dementia (FTD) linked to chromosome 17 (FTDP-17) were present in 11 cases (16%). One case (1%) showed an unusual tau pathology that could not be allocated to any of the other tau groups. Only 1 case (1%) had neuronal intermediate filament inclusion dementia. No cases with ubiquitinated, valosin-containing protein-immunoreactive intranuclear inclusion bodies of the type seen in inclusion body myopathy with Pagets disease of bone and frontotemporal dementia were seen. Clinicopathological correlation showed that any of these histological subtypes can be associated with FTD. However, for FTD with motor neurone disease (FTD+MND), semantic dementia or primary progressive aphasia (PA), the histological profile was either ubiquitin type or DLDH type; Pick-type histology was seen in only 1 case of PA. None of these latter three clinical subtypes was associated with a mutation in tau gene and FTDP-17 type of tau pathology. All cases of progressive apraxia were associated with Pick-type histology. Present data therefore indicate that, although ubiquitin pathology is the most common histological form associated with FTLD, this pathology is not tightly linked with, nor is pathologically diagnostic for, any particular clinical form of the disease, including FTD+MND.The first two authors contributed equally     

The many ways to frontotemporal degeneration and beyond

BACKGROUND: Frontotemporal degeneration (FTD) is the most common cause of dementia after Alzheimer's disease. To date, it has been addressed with intensive and intense research. OBJECTIVE: To report on the most recent findings in the biology of FTD. METHODS: Review of FTD literature. RESULTS: FTD presents with many phenotypes that span from prefrontal syndromes to lower motor neuron disease passing through temporal, parietal and extrapyramidal syndromes. FTD includes the frontotemporal lobar atrophies clinically characterised by abnormal behaviour, progressive aphasia or semantic dementia, as well as corticobasal degeneration, progressive supranuclear palsy, progressive subcortical gliosis and FTD with motor neuron disease. The molecular classification of FTD can be traced following the immunocytochemical properties of the material accumulated in neuroectodermic cells. This procedure allows the separation of FTD with tau-positive inclusions from FTD with ubiquitin-positive inclusions, and from FTD with inclusions negative for both. Genetically, seven loci (chromosomes 3p, 9q and 17q24, one locus each; 9p and 17q21, two loci each) and four genes (MAPT, PRGN, VCP, CHMP2B) have been identified. Proteins involved are tau, progranulin, VCP, CHMP2B, Progranulin TDP43, ubiquitin and the intermediate neurofilament system. Neurodegeneration is most likely due to changes in cytoskeletal structure and in ubiquitin-dependent protein degradation activity.     

Frontotemporal lobar degeneration and ubiquitin immunohistochemistry

We set out to determine the frequency of the different pathologies underlying frontotemporal degeneration (FTD) in our brain bank series, by reviewing all cases of pathologically diagnosed FTD over the last 12 years. We identified and reviewed 29 cases of FTD and classified them using the most recent consensus criteria with further histological analysis of 6 initially unclassifiable cases. Detailed histological analysis of these 6 cases revealed variable numbers of ubiquitin-positive (tau and alpha-synuclein-negative) inclusions in 5 cases, consistent with the diagnosis of frontotemporal lobar degeneration with ubiquitin-only-immunoreactive neuronal changes (FTLD-U). As a consequence of the current re-evaluation, 18 (62%) of the 29 cases with FTD have underlying pathology consistent with FTLD-U. Therefore in our brain bank series of frontotemporal degeneration, most cases were non-tauopathies with FTLD-U accounting for 62% of all the diagnoses.     

Clinicopathological and genetic correlates of frontotemporal lobar degeneration and corticobasal degeneration

Objective To correlate clinical diagnosis and genetic features with different pathological substrates in patients with frontotemporal lobar degeneration (FTLD) and corticobasal degeneration (CBD). Methods 32 cases with pathological proven FTLD or CBD were selected. Patients were classified clinically as frontotemporal dementia (FTD), progressive nonfluent aphasia (PNFA), semantic dementia (SD), CBD or FLTD with motor neuron disease (FLTDMND). Coding exons 1 and 9–13 of MAPT and exons 0–12 of the PGRN gene were screened by direct sequencing. Regarding the neuropathological findings, cases were classified as tau-positive, ubiquitinpositive tau-negative (FTLD-U), neuronal intermediate filaments inclusions disease (NIFID), dementia lacking distinctive histology (DLDH) or CBD. Results 17 patients were clinically diagnosed with FTD. Ten showed tau pathology, 3 FTLD-U, 1 NIFID and 3 DLDH. All patients clinically classified as FTLD-MND (6 patients) or SD (3 patients) were FTLD-U. Tau-positive pathology was the substrate of the three patients with PNFA. All three patients classified clinically as CBD presented neuropathologic features of CBD. The three individuals with familial history of early onset FTD and tau-positive pathology carried the P301L mutation in the MAPT gene. One out of 3 cases with FTLD-U and intranuclear inclusions carried a mutation in the PGRN gene. Conclusions We found that pathology underlying sporadic FTD is heterogeneous and not predictable. MAPT mutations and clinical diagnosis of PNFA and CBD were associated with tau-positive pathology. The presence of signs of lower MND and SD correlated with FTLD-U.A genetic study of MAPT is only recommended when familial history of early onset DFT is present. * Other members of the Catalan collaborative Study Group for FTLD are listed in the Appendix.     

Frontotemporal lobar degeneration: clinical and pathological relationships

Frontotemporal lobar degeneration (FTLD) encompasses a heterogeneous group of clinical syndromes that include frontotemporal dementia (FTD), frontotemporal dementia with motor neurone disease (FTD/MND), progressive non-fluent aphasia (PNFA), semantic dementia (SD) and progressive apraxia (PAX). Clinical phenotype is often assumed to be a poor predictor of underlying histopathology. Advances in immunohistochemistry provide the opportunity to re-examine this assumption. We classified pathological material from 79 FTLD brains, blind to clinical diagnosis, according to topography of brain atrophy and immunohistochemical characteristics. There were highly significant relationships to clinical syndrome. Atrophy was predominantly frontal and anterior temporal in FTD, frontal in FTD/MND, markedly asymmetric perisylvian in PNFA, asymmetric bitemporal in SD and premotor, parietal in PAX. Tau pathology was found in half of FTD and all PAX cases but in no FTD/MND or SD cases and only rarely in PNFA. FTD/MND, SD and PNFA cases were ubiquitin and TDP-43 positive. SD cases were associated with dystrophic neurites without neuronal cytoplasmic or intranuclear inclusions (FTLD-U, type 1), FTD/MND with numerous neuronal cytoplasmic inclusions (FTLD-U, type 2 ) and PNFA with neuronal cytoplasmic inclusions, dystrophic neurites and neuronal intranuclear inclusions (FTLD-U, type 3). MAPT mutations were linked to FTD and PGRN mutations to FTD and PNFA. The findings demonstrate predictable relationships between clinical phenotype and both topographical distribution of brain atrophy and immunohistochemical characteristics. The findings emphasise the importance of refined delineation of both clinical and pathological phenotype in furthering understanding of FTLD and its molecular substrate.     

Frontotemporal lobar degeneration: a study in Japan

Frontotemporal lobar degeneration is the most common form of cortical dementia occurring in the presenium after Alzheimer's disease. We analyzed two types of frontotemporal dementia (FTD) and semantic dementia (SD) selected from a consecutive series of outpatients based on neuropsychological symptoms, psychiatric symptoms and abnormal behavior. In our series of 134 patients with primary degenerative dementia, there were 16 cases of FTD and 6 cases of SD. Patients with subgroups of FTD and patients with SD were distinguishable only by the presence of aphasia in the latter group. They were not distinguishable from one another by other neuropsychological examinations, behavioral abnormalities or psychiatric symptoms assessed with the Neuropsychiatric Inventory.     

Epidemiology of frontotemporal lobar degeneration

A few epidemiologic studies have dealt with the prevalence of frontotemporal lobar degeneration (FTLD), including Pick's disease. The aim of this study was to review the epidemiologic studies of FTLD in western countries and to compare them with those in Japan. A community-based study of early-onset dementia in London revealed that 12% of cases with frontotemporal dementia (FTD) fulfilled the Lund-Manchester criteria in contrast to 34% of cases with Alzheimer's disease (AD) in a sample of 185 cases. The Cambridge Group has recently examined the prevalence of early-onset dementia in a community-based study. Of 108 cases, 15.7% had FTLD and 25% had AD. FTLD included 13 FTD cases, and 2 each with semantic dementia (SD) and nonfluent progressive aphasia (PA). Almost one third of cases with FTLD (29%) had a positive family history. Of our consecutive 330 outpatients with dementia (hospital setting without age limitation), 42 (12.7%) had FTLD and 215 (65.1%) had AD. In our series of patients, 22 FTD, 15 SD and 5 PA cases were identified. There was no family history in all subtypes of FTLD. Epidemiologic studies, both community-based and hospital-based, demonstrate that FTLD is a more common cause of early-onset dementia than previously recognized. Regarding the subtypes of FTLD, in Japan, compared with the data from the UK, FTD is less common, SD may be more common and PA is equally common. The reason for this discrepancy is supposed to be mainly based on the role of heredity.     

The neuropathology and clinical phenotype of FTD with <Emphasis Type="Italic">progranulin</Emphasis> mutations

Mutations in the progranulin gene (PGRN), on chromosome 17q21, have recently been identified as a major cause of familial frontotemporal dementia (FTD). These cases have a characteristic pattern of neuropathology that is a distinct subtype of frontotemporal lobar degeneration with ubiquitinated inclusions (FTLD-U), with lentiform neuronal intranuclear inclusions being a consistent feature. There is no abnormal accumulation of PGRN protein in the brain and immunohistochemical and biochemical analysis indicates that the ubiquitinated pathological protein is TDP-43. In these families, FTD is inherited in an autosomal dominant fashion with high penetrance. The clinical phenotype is usually a combination of behavioural abnormality and language disturbance that is most often a form of primary progressive aphasia. Mild parkinsonism is common but motor neuron disease is notably rare. Marked variation in the disease course and clinical features are common, not only between families with different mutations, but also within individual families. This degree of clinical variability makes it difficult to predict which cases of familial FTD will turn out to have a PGRN mutation.     

Frontotemporal dementia

Frontotemporal dementia (FTD) is an uncommon but important form of degenerative disease. It may make up 50% of dementia cases presenting before age 60. The symptoms are related to the anatomic areas affected. Neary divided the clinical syndromes into "frontotemporal dementia," "progressive nonfluent aphasia," and "semantic dementia." However, the pathology may extend beyond the frontal and temporal lobes and additional symptoms may be found. Although most cases are sporadic, some cases are genetic. The best-known genetic mutation causing FTD is frontotemporal dementia with parkinsonism, linked to the microtubule-associated protein tau on chromosome 17. There are other known genes and chromosome loci related to FTD. The most common pathology found is frontotemporal degeneration with ubiquitin inclusions. In contrast, FTD with Pick bodies is rare. Although there are strategies to help patients and their families, there is no known treatment for the disease.