Interestingly, despite abnormal CSF orexin levels (<200 pg/ml) in all the three groups (PD with RBD: 177.69 ± 46.04 pg/ml; PD without RBD: 177.31 ± 29.4 pg/ml and iRBD: 166.23 ± 40.62 pg/ml), orexin levels in the three groups were not reported significantly lower than in the control group [56]. The gene discussed is HCRT; the disease is Parkinson disease.