MAPT and tauopathy: Furthermore, Bieniek et al [6] noted excessive tau pathology in a higher proportion of patients with FTLD-TDP associated with an expansion in C9orf72, and in others with FTLD-TDP with no known mutation, when compared to cases of FTLD-TDP with GRN mutations and suggested that some forms of TDP-43 proteinopathy might favour or promote the development of tauopathy.