ATP13A2 and red-green color blindness: While a VSGP is required for the diagnosis of PSP, a growing list of disorders also include this feature, such as corticobasal degeneration (CBD) or corticobasal syndrome (CBS) [32, 33], frontotemporal dementia [34], Creutzfeldt-Jakob disease [35–39], Kufor-Rakeb syndrome (PARK9 due to ATP13A2 mutations) [40, 41], Perry syndrome due to DCTN1 mutations [42], Niemann-Pick type C [15], Whipple’s disease [43], and Gaucher’s disease type 3 (horizontal saccades can also be affected, or even more severe) [44], among others.