GRN and Cognitive impairment: Given that pathogenic variants of GRN are rare in Korean patients with FTD [19, 20] and mutations of GRN are associated with highly variable clinical phenotypes including amnestic syndromes (AD dementia, mild cognitive impairment (MCI), hippocampal sclerosis), corticobasal syndrome, and amyotrophic lateral sclerosis, as well as FTD syndromes [21, 22], we hypothesized that screening tests for serum PGRN in various neurodegenerative dementia would be relevant for identifying Korean GRN mutation carriers who possibly presented with various neurodegenerative dementia other than FTD syndromes.