Three exosomal proteins, namely clusterin, complement C1r subcomponent, and apolipoprotein A1, were examined across PD stages and proposed as potential indicators and trackers of PD progression.[168] A study compared exosome levels from neurons, astrocytes, and oligodendrocytes in the plasma of PD, MSA, PSP, and healthy participants.[169] They found neuron‐derived exosomes significantly elevated in PD patients compared to healthy controls and MSA. Here, APOA1 is linked to Parkinson disease.