Several studies have examined CSF markers of neurodegeneration in PD (eg, α‐syn, beta‐amyloid [Aβ] 1‐40 and 1‐42, total tau [t‐tau], and phosphorylated tau [p‐tau] concentrations), but most studies focus on either de novo PD patients (eg, deprenyl and tocopherol antioxidative therapy of parkinsonism [DATATOP] or Parkinson's Progression Markers Initiative [PPMI]), or specifically on cognitive measures in PD cohorts.1, 11, 12, 13, 14, 15, 16 Of this work, the prevailing evidence is that CSF α‐syn is reduced in PD and that subspecies of α‐syn oligomers may distinguish PD from controls. The gene discussed is MAPT; the disease is Parkinsonism.