Recently, the expanded GGGGCC (G4C2) hexanucleotide repeat in intron 1 of C9orf72 has been confirmed to cause striatal impairment with TDP-43 accumulation in the FTDP patients, which can be clearly distinguished from Parkinson disease-related mechanisms by the absence of α-synuclein-positive Lewy bodies or Lewy neurites in the substantia nigra9,21,22. The gene discussed is C9orf72; the disease is Parkinson disease.