MAPT and supranuclear palsy, progressive, 1: Progressive supranuclear palsy (PSP) is a progressive neurodegenerative condition and the most common cause of atypical parkinsonism, with an estimated prevalence of 5 to 7 per 100,000.1 The pathology of PSP is centered on the structural microtubule‐associated protein tau, encoded by the MAPT gene located on chromosome 17.