Although α-synuclein SAAs are highly sensitive and specific for diagnosing PD2 and MSA,3 neuropathological studies have found that patients with PSP and corticobasal degeneration (CBD) also exhibit α-synuclein protein pathology,23,67,68 potentially limiting the specificity of α-synuclein SAAs in the differential diagnosis of these diseases. The gene discussed is PCSK1N; the disease is multiple system atrophy.