Atypical frontotemporal lobar degeneration with ubiquitin-positive, TDP-43-negative neuronal inclusions.
Frontotemporal lobar degeneration with ubiquitinated inclusions (FTLD-U) is the most common neuropathology associated with the clinical syndrome of frontotemporal dementia (FTD). Recently, TDP-43 was identified as the ubiquitinated pathological protein in both FTLD-U and sporadic amyotrophic lateral sclerosis. Although a number of studies have now confirmed that most sporadic and familial cases of FTLD-U are TDP-43 proteinopathies, there are exceptions. We describe six cases of early onset FTD with FTLD-U pathology that was negative for TDP-43, which we refer to as 'atypical' FTLD-U. All cases were sporadic and had very early onset FTD (mean age = 35 years), characterized by severe progressive psychobehavioural abnormalities in the absence of significant aphasia, cognitive-intellectual dysfunction or motor features. The neuropathological features were highly consistent, with small, round, neuronal cytoplasmic inclusions that were immunoreactive for ubiquitin (ub-ir), but negative for tau, alpha-synuclein, intermediate filaments and TDP-43. Cytoplasmic inclusions were most numerous in the neocortex, dentate granule cells and hippocampal pyramidal neurons. Ub-ir neuronal intra-nuclear inclusions were also present in neocortical and hippocampal neurons and had the unusual appearance of straight, curved or twisted filaments. We believe that these cases represent a new entity that is clinically and pathologically distinct from all currently recognized subtypes of FTLD. Moreover, the existence of such cases indicates that the designations of 'FTLD-U' and 'TDP-43 proteinopathy' should not be considered to be synonymous.
Mackenzie
Ian R A
IR
Department of Pathology, University of British Columbia, Vancouver General Hospital, 855 West 12th Avenue, Vancouver, British Columbia, V5Z 1M9 Canada. ian.mackenzie@vch.ca
Foti
Dean
D
Woulfe
John
J
Hurwitz
Trevor A
TA
D000328:Adult; D017668:Age of Onset; D001921:Brain / Q000473:pathology; D004268:DNA-Binding Proteins / Q000032:analysis*; D003704:Dementia / Q000378:metabolism* / Q000473:pathology / Q000523:psychology; D005260:Female; D006801:Humans; D002479:Inclusion Bodies / Q000737:chemistry* / Q000473:pathology; D008297:Male; D001523:Mental Disorders / Q000209:etiology; D009474:Neurons / Q000737:chemistry* / Q000473:pathology; D025801:Ubiquitin / Q000032:analysis*
D004268:DNA-Binding Proteins; D025801:Ubiquitin