Loss of orexin neurons are widely implicated in dysregulated sleep in patients with narcolepsy and has been observed in patients with PWS as well (Vgontzas et al., 1996; Chemelli et al., 1999; Mignot et al., 2002; Omokawa et al., 2016). The gene discussed is HCRT; the disease is Prader-Willi syndrome.