MAPT and psychotic disorder: This is consistent with prior studies showing they occur commonly in C9orf72 mutation carriers,6 although not uniquely and can be present in the other genetic groups.7 32 In the current study, hallucinations and delusions were present only infrequently in C9orf72 mutation carriers in the presymptomatic period, increasing in frequency when entering the symptomatic phase.33 Psychosis-type symptoms were least frequent and mildest in MAPT mutation carriers, although were still present, suggesting that these symptoms are not pathognomonic of a particular genetic subtype.