Semantic dementia with lower motor neuron disease showing FTLD-TDP type 3 pathology (sensu Mackenzie).

We describe a case of frontotemporal lobar degeneration with semantic dementia and lower motor neuron disease. A 63-year-old man presented with the full clinical picture of semantic dementia, including semantic anomia, surface alexia, lexical agraphia, associative agnosia, prosopagnosia and phonagnosia. Flaccid dysarthria, bulbar dysphagia and fasciculations developed 7 years after onset, followed by death within a year. The neuropathological examination showed heavy neuronal loss in the anterior temporal lobe cortex, dorsal vagal and hypoglossal nuclei and anterior horns of the spinal cord. Ubiquitin- and TDP-43-positive cytoplasmic inclusions were abundant in layer II of affected cortices and in granular cells of the hippocampal dentate gyrus, whereas dystrophic neurites were sparse and intranuclear inclusions absent. It is concluded that FTLD-TDP type 3 can be associated with semantic dementia and lower motor neuron disease in combination.