SORL1 and frontotemporal dementia: This mutation was also found in an asymptomatic at risk member of the third generation (HIII2), aged 42 years (average age at onset in Family H is 68 years) and was not detected in another familial member, displaying FTD with memory onset, suggesting that SORL1 (p.R744X) may influence AD with language problems and PPA and that there may be additional genetic modifiers responsible for different phenotypic manifestations.