36 of FTLD-FUS. Twenty-three cases for which DNA was available (21 FTLD-FUS and 2 FTLD-UPS) were screened for CHMP2B mutations. Fifteen FTLD-FUS cases were screened for FUS mutations and a further six have been reported previously as FUS mutation negative [37]. Patients were considered to have a family history if a ﬁrst- or second- degree relative had dementia. This study was approved by the UCL Institute of Neurology and National Hospital for Neu- rology and Neurosurgery Local Research Ethics Committee. Histopathology All cases were stained for TDP-43, ubiquitin and a-intern- exin or neuroﬁlament proteins according to local protocols at each centre [2, 12, 21, 27, 29, 39, 40, 42, 47, 53]. Expe- rienced neuropathologists in each centre analysed the sections to give the neuropathological diagnosis. FUS staining was subsequently performed on frontal cortex and hippocampus for all cases. As previously described, FUS staining is sensitive to length of ﬁxation [37]. Therefore, at least two antibodies (Sigma HPA008784 and Bethyl Labo- ratories A300-302A) were used for all cases examined and antibody concentrations optimised for each case by ensuring physiological FUS staining was visible, as recommended in the original description of FTLD-FUS [37]. To further ensure inter-centre reliability 26 cases, including the three remaining FTLD-UPS cases, were stained in one of two laboratories which ﬁrst reported FTLD-FUS (IRM or MN). Genetic analysis Genomic DNA was extracted from brain tissue using standard phenol–chloroform extraction, or DNA extracted from brain or blood was directly provided by the contrib- utor. The entire open reading frame and exon–intron boundaries of CHMP2B and FUS were sequenced, except for three cases in which FUS exons 14 and 15 only were sequenced. Primers and conditions for CHMP2B sequenc- ing have been described previously [49]; conditions for FUS sequencing are available on request. Sequences were analysed using the SeqScape software Version 2.5 (Applied Biosystems, Foster City, CA, USA). Results Neuropathology A total of 37 ubiquitin-positive, tau- and TDP-43-negative cases were examined. 92% (34/37) of cases were charac- terised by neuronal cytoplasmic and intranuclear inclusions (NIIs) which were immunoreactive for FUS, corresponding to the aFTLD-U subtype of FTLD-FUS. The NIIs were as 123 Acta Neuropathol (2010) 120:33–41 previously described, having an unusual morphology, which can be long and straight, curved or twisted [29, 42]. Striatal degeneration was present in 100% (27/27) of aFTLD-U cases and hippocampal sclerosis was present in 97% (29/30) of cases. 8% (3/37) were characterised by ubiquitin-positive neuronal cytoplasmic inclusions (NCIs) which were FUS-negative, i.e. FTLD-UPS. Genetics Sequencing of the CHMP2B gene in all cases for which DNA was available revealed no further coding mutations. Two synonymous coding variants were identiﬁed in three FTLD-FUS cases: c.27C[T, p.Thr9Thr and c.372A[C, p.Thr124Thr. These two variants were each observed in the heterozygous state but always together, suggesting they could be in linkage disequilibrium. None of these variants has been previously reported, but as they do not lead to an amino acid change, they are unlikely to be pathogenic. Therefore, CHMP2B mutation-positive cases comprise a distinct genetic subgroup of FTLD-UPS. No mutations were identiﬁed in FUS in any case. Demographics Onset Age at onset data was available for 33 aFTLD-U cases. The mean age of onset was 41.2 years (standard deviation 9.3 years). The three FTLD-UPS cases had a mean age of onset of 50.3 years (standard deviation 4 years). Disease duration Disease duration data were available for 33 aFTLD-U cases. Mean disease duration was 7.7 years (standard deviation 3.2 years). Disease duration data were available for only two of the three FTLD-UPS cases and were 4 and 11 years, respectively. Sex Of the aFTLD-U cases, 47% (16/34) were female and all three FTLD-UPS cases were female. Family history One aFTLD-U case (3%, 1/34) had a family history and 2/3 of the FTLD-UPS cases had positive family histories. Clinical features The clinical features of several aFTLD-U cases have pre- viously been reported [21, 29, 42, 46] and analysed together,