A practical problem in trial design for FTD spectrum disorders is recruiting enough patients to test candidate therapeutics as FTD is much less common than AD, with an estimated prevalence of 15/100,000 and approximately 10–20% of cases being caused by mutations in C9orf72, GRN, and MAPT genes [4, 7, 42]. The gene discussed is MAPT; the disease is Alzheimer disease.