Frequency of tau gene mutations in familial and sporadic cases of non-Alzheimer dementia

Background: Mutations in the tau gene have been reported in families with f rontotemporal dementia (FTD) linked to chromosome 17. It remains uncertain how commonly such mutations are found in patients with FTD or non-Alzheimer dementia with or without a positive family history. Objective: To determine the frequency of tau mutations in patients with non -Alzheimer dementia. Patients and Methods: One hundred one patients with non-Alzheimer, nonvascu lar dementia, most thought to have FTD. Of these, 57 had a positive family history of dementia. Neuropathologic findings were available in 32. The tau gene was sequenced for all exons including flanking intronic DNA, portions of the 3' and 5' untranslated regions, and at least 146 base pairs in the intron following exon 10. Results: Overall, the frequency of the tau mutations was low, being 5.9% (6 /101) in the entire group. No mutations were found in the 44 sporadic cases . However, 6 (10.5%) of the 57 familial cases and 4 (33%) of the 12 familia l cases with tau pathologic findings had mutations in the tau gene. The mos t common mutation was P301L. Conclusions: We conclude that tau mutations are uncommon in a neurology ref erral population with non-Alzheimer dementia, even in those with a clinical diagnosis of FTD. However, a positive family history and/or tau pathologic findings increase the likelihood of a tau mutation. There must be other ge netic and nongenetic causes of FTD and non-Alzheimer dementia, similar to t he etiologic heterogeneity present in Alzheimer disease.