Frontotemporal dementia (FTD) is a progressive neurodegenerative disorder characterized by the predominant degeneration of the frontal and temporal cortices, with associated deficits in behavior, executive function, and/or language.1 Haploinsufficiency of the progranulin (PGRN; GRN) gene accounts for 5%–20% of familial FTD and results in nuclear depletion and cytosolic accumulation of the RNA-binding protein TAR DNA-binding protein 43 (TDP-43), which is encoded by the gene TARDBP. The gene discussed is GRN; the disease is frontotemporal dementia.