Finally, although we do not understand the relationship between the MAPT locus and Parkinson disease, it is worth remembering that while LRRK2 mutations usually give rise to α-synuclein pathology, they sometimes give rise to tangle pathology (Zimprich et al., 2004) and that, while APP mutations usually give rise to tangle pathology, they sometimes give rise to Lewy body pathology (Hardy 1994). The gene discussed is MAPT; the disease is Parkinson disease.