It seems it's possible to get it from hypocretin deficiency via other routes like brain trauma, but they are confident enough to put this explanation in the DSM-5:
> Narcolepsy-cataplexy nearly always results from the loss of hypothalamic hypocretin (orexin)-producing cells, causing hypocretin deficiency (less than or equal to one-third of control values, or 110 pg/mL in most laboratories). Cell loss is likely autoimmune, and approximately 99% of affected individuals carry HLA-DQBl06:02 (vs. 12%-38% of control subjects). Thus, checking for the presence of DQB106:02 prior to a lumbar puncture for evaluation of CSF hypocretin-1 immunoreactivity may be useful.
https://ia800900.us.archive.org/0/items/info_munsha_DSM5/DSM...
pg 374, par 4 (pg 409 if using a PDF reader).
The author also describes dreaming while awake, and specifically just before sleep. Surely this is something that happens to everyone, no? My mind goes crazy when I'm about to fall asleep, and that's how I normally know I'm going to be asleep in the next minute or two. Typically I'll start thinking about strange interconnected things and people, objects and voices will randomly appear in my consciousness. Is this honestly not normal? Isn't that just what happens when you drift off to sleep?
> "Although experiencing a hallucination might prompt confusion or fear, hypnagogic hallucinations are relatively common. Hypnagogic hallucinations are a common symptom of narcolepsy, but can also occur in people who do not have narcolepsy. In fact, one study found that 37% of people report experiencing hallucinations as they fall asleep."
Source: https://www.sleepfoundation.org/how-sleep-works/hypnagogic-h...
Their association with narcolepsy is one of several features, and it occurs more frequently and often during daytime naps in patients with narcolepsy:
> Hypnagogic states are not only an associated feature of narcolepsy, but they also are favourable for a diagnosis. Accordingly, the prevalence of hypnagogic states was higher in patients with narcolepsy than controls (Bosch et al., 2012; Fortuyn et al., 2009). Moreover, patients with narcolepsy are also more prone to experience daytime hypnagogia (Fortuyn et al., 2009), most likely due to excessive daytime sleepiness.
Source: https://pmc.ncbi.nlm.nih.gov/articles/PMC10078162/