GRN and Alzheimer disease: Unusual microglial morphologies such as thin, elongated cells known as rod-shaped microglia, and also hypertrophic microglia, which have short, thickened, bushy processes, are present in AD cases [13, 55], and rod-shaped microglia have been noted in FTLD-TDPA due to GRN or C9orf72 mutations [42, 53] and sporadic FTLD-TDPA cases [42].