Geneticists then sequenced genes near MAPT and were rewarded by finding mutations in the progranulin gene (PGRN), which is located a mere 1.7 Mb away from MAPT. In one patient series, PGRN mutations accounted for at least 11% of all FTD cases and 26% of familial FTD cases. Here, MAPT is linked to frontotemporal dementia.