Patients with NT1 have cataplexy, a transient muscle tone loss often triggered by emotion, and/or orexin (hypocretin) deficiency (≤110 pg/mL, or less than one-third of mean values from individuals without narcolepsy), whereas patients with NT2 do not have cataplexy and have normal cerebrospinal fluid orexin levels [1]. Here, HCRT is linked to narcolepsy.