GRN and primary progressive aphasia: The top 10 clusters that reflect the knowledge base and research progress in FTD are #0 semantic dementia, #1 FTDP-17, #2 TDP-43, #3 C9orF72, #4 progranulin, #5 protein aggregation, #6 biomarkers, #7 FUS, #8 primary progressive aphasia, and #9 psychosis.