Mutations in quite a few genes have been linked to FTM and the list is growing.

One is MAPT, which codes for a protein called Tau - mutations in this gene are linked to FTM with parkinsonism.

Another is GRN, which codes for a protein called Granulin. These mutations account for about 25% of FTM cases and have high penetrance, which means that somebody with it is very likely to get the disease.

Mutations in the VCP gene, coding for Valosin-containing protein, has been implicated in a disease called multisystem proteinopathy, which can include FTM-like signs.

In theory screening for these mutations is easy (it would take somebody in my research lab about a week or so) but I don't know how available it is in commercial genetic screening labs.