SORL1 and frontotemporal dementia: Moreover, we report one SORL1 mutation in the valosin-containing protein (VCP) domain (p.R744X) that was associated to AD with severe language impairment and PPA and was not detected in a member of the same family that had been initially diagnosed with AD and successively with FTD with memory onset (Table 3, Fig. 2A, B).