Distinct pathological subtypes of FTLD-FUS.
Most cases of frontotemporal lobar degeneration (FTLD) are characterized by abnormal intracellular accumulation of either tau or TDP-43 protein. However, in ~10% of cases, composed of a heterogenous collection of uncommon disorders, the molecular basis remains to be uncertain. We recently discovered that the pathological changes in several tau/TDP-43-negative FTLD subtypes are immunoreactive (ir) for the fused in sarcoma (FUS) protein. In this study, we directly compared the pattern of FUS-ir pathology in cases of atypical FTLD-U (aFTLD-U, N = 10), neuronal intermediate filament inclusion disease (NIFID, N = 5) and basophilic inclusion body disease (BIBD, N = 8), to determine whether these are discrete entities or represent a pathological continuum. All cases had FUS-ir pathology in the cerebral neocortex, hippocampus and a similar wide range of subcortical regions. Although there was significant overlap, each group showed specific differences that distinguished them from the others. Cases of aFTLD-U consistently had less pathology in subcortical regions. In addition, the neuronal inclusions in aFTLD-U usually had a uniform, round shape, whereas NIFID and BIBD were characterized by a variety of inclusion morphologies. In all cases of aFTLD-U and NIFID, vermiform neuronal intranuclear inclusions (NII) were readily identified in the hippocampus and neocortex. In contrast, only two cases of BIBD had very rare NII in a single subcortical region. These findings support aFTLD-U, NIFID and BIBD as representing closely related, but distinct entities that share a common molecular pathogenesis. Although cases with overlapping pathology may exist, we recommend retaining the terms aFTLD-U, NIFID and BIBD for specific FTLD-FUS subtypes.
Department of Pathology, Vancouver General Hospital, University of British Columbia, BC, Canada. ian.mackenzie@vch.ca
Ian R A
IR
Mackenzie
David G
DG
Munoz
Hirofumi
H
Kusaka
Osamu
O
Yokota
Kenji
K
Ishihara
Sigrun
S
Roeber
Hans A
HA
Kretzschmar
Nigel J
NJ
Cairns
Manuela
M
Neumann
D001491:Basophils / Q000473:pathology; D001921:Brain / Q000378:metabolism* / Q000473:pathology*; D004268:DNA-Binding Proteins / Q000378:metabolism; D005260:Female; D057174:Frontotemporal Lobar Degeneration / Q000145:classification / Q000378:metabolism / Q000473:pathology; D006801:Humans; D045586:Intranuclear Inclusion Bodies / Q000378:metabolism / Q000473:pathology; D008297:Male; D019636:Neurodegenerative Diseases / Q000378:metabolism / Q000473:pathology; D034702:RNA-Binding Protein FUS / Q000378:metabolism*; D018709:Statistics, Nonparametric; D016875:tau Proteins / Q000378:metabolism
D004268:DNA-Binding Proteins; D034702:RNA-Binding Protein FUS; D016875:tau Proteins