Type 1 [ 2 38 ± 11 (14) 41 ± 3 (16) 42 ± 8 (20) 44 (10) 44 ± 4 (14) 38 (10) Type 1 [ 2 48 (5) 48 (7) 33 ± 13 (50) 46 (17) 32 ± 10 (44) 7 (17) Type 2 [ 1 70 ± 18 (46) 77 ± 9 (44) 78 ± 14 (70) 90 ± 7 (70) 75 ± 14 (43) 61 ± 4 (20) Type 2 [ 1 84 ± 12 (47) 80 ± 15 (73) 75 ± 14 (50) 83 ± 4 (83) 65 ± 12 (25) (0) 665 Type 2 only (40) (40) (10) (20) (22) (0) (48) (20) (0) (0) (0) (50) Type 2 only Brain region Neocortex Limbic areas Striatum Thalamus Hypothalamus ? Brainstema Cerebellum Brain region Neocortex Limbic areas Striatum Thalamus Hypothalamus ? Brainstem Cerebellum Type 1 only (0) (0) (0) (0) (21) (70) Type 1 only (0) (0) (0) (0) (8) (33) Numbers in brackets express the % of samples showing each of the 4 proﬁles in the listed brain regions a Samples from the brainstem were not available in three cases Table 3 Regional relative amounts (in % ± SD) of PrPSc type 2 in MV 2C?1 cases (N = 3) Acta Neuropathol (2009) 118:659–671 Table 2 Regional relative amounts (in % ± SD) of PrPSc type 2 in MM 2C?1 subjects (N = 5) Numbers in brackets express the % of samples showing each of the 4 PrPSc proﬁles in the listed brain regions VV subjects Six VV cases with concurrent PrPSc types 1 and 2 were found. PrPSc type 2 was always dominant and detectable in almost all samples. By contrast, type 1 was only present focally in the cerebral cortex, in the striatum or in both. In two cases, however, PrPSc type 1 was seen in most samples from cerebral cortex and striatum and in a single case, it showed an even more widespread accumulation involving all the cerebral cortical samples, the striatum, amygdala, hippocampus, hypothalamus and thalamus (Fig. 4a). When concurring, type 2 was predominant over type 1 in 76% of samples, while type 1 had a stronger signal than type 2 in the remaining 24%. The mean total type 1 ‘‘load’’ in VV 2?1 was 9.4% (range 1.5–38%). Although clearly distinguishable from a type 1 and 2 concurrence, also the PrPSc type 2 proﬁle in VV subjects was sometimes characterized by a doublet comprising a *18.5 kDa fragment in addition to the typical 19 kDa band (Fig. 4b). These two bands concurred in the cere- bellum in all cases, in the thalamus in 50% of them and in the midbrain in 18%. Since epitope mapping indicated that the 18.5 peptide, like the 19 kDa fragment, has an intact C- terminus (data not shown), the two fragments likely differ in their N-terminal PK cleavage site (i.e. the 18.5 fragment is further cleaved beyond residues 97–99). Molecular-phenotypic correlations: the pathological phenotype The pathological phenotype in MM/MV 1?2C and MM/ MV 2?1C subjects displayed varying relative amounts of features as previously described in the pure MM/MV 1 and MM/MV 2C subtypes [30, 33]. The lesion proﬁle in MM/ MV 1?2C largely overlapped with that of pure MM/MV 1 cases, with the exception of the cerebellum, which was less affected relatively to the cerebral cortex (Fig. 5, and data not shown). Histopathologic hallmarks in these cases were (a) ‘‘morula-like’’, sometimes referred to as ‘‘grape-like’’, conﬂuent foci of spongiform degeneration with large vac- uoles in addition to the classic microvacuolation, and (b) a mixed synaptic/perivacuolar or coarse pattern of PrP deposition (Fig. 6a, b). With the exception of one case, in which, only the type 1 protein could be demonstrated by immunoblotting even after the 1E4 staining, in this group we found a 100% correlation between the large vacuoles and the perivacuolar staining on one hand and the PrPSc type 2 detection by immunoblotting on the other. The extension of the perivacuolar or coarse PrP staining, co- localizing with the conﬂuent vacuoles varied signiﬁcantly from case to case and was overall more common in the cerebral cortex than in subcortical areas (Fig. 7). The temporal, parietal and occipital cortices were the most 123