Incidence and morphology of secondary TDP-43 proteinopathies: Part 2.

Transactivation (TAR) DNA binding protein 43 kDa (TDP-43) inclusions frequently occur as a comorbid pathology in several neurodegenerative disorders, including Alzheimer's disease, Huntington's disease, Lewy body disease, and progressive supranuclear palsy, and may appear in association with nondegenerative neurological etiology, for example neoplastic, paraneoplastic, traumatic, or infectious. Relationships between various pathological proteins and mechanisms associated with TDP-43-induced neurodegeneration are still not fully understood. Thus, overlap of distinct neuropathological mechanisms frequently leads to greater brain atrophy and a more severe clinical course, suggesting the importance of co-pathologies in ante-mortem diagnosing and treatment. The present review aims to discuss the incidence, morphology, and role of TDP-43 pathology in the context of other dominant, hallmark pathologies, referred to as secondary TDP-43 proteinopathies. The previous part (Part 1) focused on common neurodegenerative diseases, including Alzheimer's disease, Huntington's disease, and Lewy body disease, while the present part (Part 2) discusses TDP-43 pathology in rare neurodegenerative diseases and neurological diseases with nondegenerative etiology.