Extracellular vesicles (EVs) derived from tissues affected by disease have emerged as a rich source of biomarkers.4,5 Furthermore, immunocapture of presumed neuronally derived circulating EVs using anti-L1CAM (L1EVs) has been applied to a number of neurologic diseases as a proxy biomarker of brain pathology.6 Despite this extensive literature, the precise relevance of L1EVs in PD diagnostics remains unresolved. Here, L1CAM is linked to Parkinson disease.