Abstract
Neuropathological diagnostic criteria of neurodegenerative disorders are based on the presence of specific lesions in the brain tissue that correlate with clinical symptoms. Concomitant neurodegenerative disorders correspond to a combination of two (or more) different fully developed diseases in one patient.
Concomitant neurodegenerative pathology stays for the presence of a definite neurodegeneration and deposits specific for another, but not fully developed, disease. Frequent overlaps include Alzheimer's disease (AD) and alpha-synuclein inclusions.
In AD, protein TDP-43 may co-aggregate but it is not clear whether this is an atypical but isolated AD, or an overlap of AD with early frontotemporal lobar degeneration. Comorbidities of AD and tauopathies are relatively rare.
In Creutzfeldt-Jakob disease, concomitant AD or Lewy body dementia may occur. A combination of vascular pathology with a primary neurodegeneration (mostly Alzheimer's disease or Lewy body dementia) is historically called mixed dementia.
Overlap of neuropathologically confirmed neurodegenerations may lead to atypical and unusual clinical presentations, illustrated with examples and references to published case reports from our patient cohort