o-α-synuclein concentration in CSF from PD patients was consistently higher, showing a good diagnostic accuracy in distinguishing PD patients from healthy subjects [13,14,15,16], but there is less evidence in serum or plasma [17,18], with a couple of studies showing a significant increase in PD patients [19,20] and others showing values comparable to or even lower than controls [11]. The gene discussed is SNCA; the disease is Parkinson disease.