A recent study employed single-molecule array (Simoa), an ultra-sensitive technology, to quantitate very low concentrations (picomolar to femtomolar) of α-synuclein protofibrils (PFs) in CSF of PD patients and observed an increased concentration of α-synuclein PFs in PD patients (von Euler Chelpin et al., 2020). Here, SNCA is linked to Parkinson disease.