We investigated the clinicopathological characteristics of 29 autopsy cases of ALS with cognitive or behavioral abnormalities and evaluated the association between clinical symptoms and comorbid pathologies such as Alzheimer’s disease (AD), argyrophilic grain disease (AGD), dementia with Lewy bodies (DLB), and primary age-related tauopathy (PART), as well as the presence of cortical TDP-43 pathology. Here, TARDBP is linked to early-onset autosomal dominant Alzheimer disease.