Comment by exhypothesi

It's easy to miss! The only reason I know is because of all of the research I've done into my Idiopathic Hypersomnia diagonsis. Mignot is well-respected because of his research.

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).