Psychotic symptoms in frontotemporal dementia with TDP‐43 tend to be associated with type B pathology

Aims Psychotic symptoms are increasingly recognized as a distinguishing clinical feature in patients with dementia due to frontotemporal lobar degeneration with TDP‐43 pathology (FTLD‐TDP). Within this group, carriers of the C9orf72 repeat expansion are particularly prone to develop delusions and hallucinations. Methods The present retrospective study sought to provide novel details about the relationship between FTLD‐TDP pathology and the presence of psychotic symptoms during life. Results We found that FTLD‐TDP subtype B was more frequent in patients with psychotic symptoms than in those without. This relationship was present even when corrected for the presence of C9orf72 mutation, suggesting that pathophysiological processes leading to the development of subtype B pathology may increase the risk of psychotic symptoms. Within the group of FTLD‐TDP cases with subtype B pathology, psychotic symptoms tended to be associated with a greater burden of TDP‐43 pathology in the white matter and a lower burden in lower motor neurons. When present, pathological involvement of motor neurons was more likely to be asymptomatic in patients with psychosis. Conclusions This work suggests that psychotic symptoms in patients with FTLD‐TDP tend to be associated with subtype B pathology. This relationship is not completely explained by the effects of the C9orf72 mutation and raises the possibility of a direct link between psychotic symptoms and this particular pattern of TDP‐43 pathology. FTLD‐TDP type B pathology tends to be more frequent in patients with psychotic symptoms than in those without. This relationship is only partially explained by the association of type B pathology with C9orf72 hexanucleotide expansion. Within subjects with FTLD‐TDP type B pathology, psychotic symptoms tended to be associated with a greater burden of TDP‐43 pathology in the white matter and a lower burden in lower motor neurons.