Additionally, rare secondary forms of narcolepsy, both with and without cataplexy, exist, for instance in demyelinating diseases, in paraneoplastic encephalitis, or associated with genetic syndromes (e.g. Niemann‐Pick type C, mutations of DNA‐methyltransferase type‐I), with CSF orexin levels that can be normal, reduced or intermediate (Dauvilliers, Bauer et al., 2013; Moghadam et al., 2014; Nishino & Kanbayashi, 2005). Here, HCRT is linked to narcolepsy.