Based on the current data showing little to no binding of [18F]-AV-1451 in the majority of DM1 participants in this sample, and only strong binding in the patient with possible concomitant AD, we conjecture that [18F]-AV-1451 either does not bind to DM1-specific Tau conformations, or that it is not sufficiently sensitive to detect the low levels of Tau pathology that are present in many or most DM1 participants. The gene discussed is MAPT; the disease is myotonic dystrophy type 1.