In DLB and PDD, spread and increased burden of α‐syn pathology in cortical and limbic regions correlate with cognitive decline.4, 5, 6 Concomitant Alzheimer's disease (AD) is common at autopsy in DLB, but also in PDD7, 8 and AD‐related tau and β‐amyloid (Aβ) pathologies have been shown to contribute independently to dementia.4, 9 This suggests that it will be important to identify the pathological substrates of cognitive decline when selecting patients with DLB or PDD for future clinical trials of drugs targeting specific pathologies. This evidence concerns the gene MAPT and Mental deterioration.