Of those with definite bvFTD nine had mutations in the MAPT gene (five harbored the intron 10 + 16 mutation, two harbored the exon 13 R406W mutation, one harbored the exon 10 P301S mutation, and one harbored a novel mutation in exon 12 resulting in a single amino acid substitution at codon 351 (Q351R)), four had mutations in C9ORF72 and one patient who subsequently died was found to have Pick's disease pathology at postmortem. This evidence concerns the gene MAPT and frontotemporal dementia.