In a study examining frontotemporal dementia (FTD), a patient group carrying mutation in one of the three genes (C9orf72, GRN, and MAPT), presymptomatic individuals carrying mutations, and a healthy control group that did not carry any mutation were evaluated, and the expression levels of miR-204 in exosomes obtained from cerebrospinal fluid were shown to be lower in the symptomatic patients compared to the other groups [53]. The gene discussed is C9orf72; the disease is frontotemporal dementia.