Kang et al. [19] (New York, USA) explored the possibility of a correlation between mGluR5 and PD using the selective mGluR5 PET probe 18F-FPEB in nine patients with PD compared with a control group, and showed a significant enhancement of binding of the radiotracer in PD patients compared with the healthy controls. The gene discussed is GRM5; the disease is Parkinson disease.