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Editor-Thank you for publishing these fascinating case reports of
narcolepsy. Sleep disorders certainly need some more media coverage,
incl. in professional journals, to come to the light of medical attention.
However, I am a little perplexed that the authors make no mention
whatsoever about the hypocretin/orexin story, more than one year after the
discovery of their link to narcolepsy. Instead, the authors chose to
focus on the association with various HLA types - a problematic premise
given the discovery of the genetic link to hypocretin/orexin and the
absence of any HLA association in various canine models.
Despite their appropriate word of caution in the discussion that "the
possession of this allele is neither necessary nor sufficient for the
disorder", in the presentation of each case they conclude that the
presence of the HLA types is "consistent with narcolepsy". This is in my
view an overly optimistic statement and may mislead some clinicians to
conclude that HLA typing is a useful diagnosic tool for narcolepsy - which
it is not. Absence of the appropriate HLA type may serve as some evidence
against the disorder, but presence of the allele adds barely any
diagnostic certainty, given the relatively high pre-test probability in
the selected clinic population on whom the HLA typing would be undertaken.
What about the hypocretin/orexin story?
Editor-Thank you for publishing these fascinating case reports of
narcolepsy. Sleep disorders certainly need some more media coverage,
incl. in professional journals, to come to the light of medical attention.
However, I am a little perplexed that the authors make no mention
whatsoever about the hypocretin/orexin story, more than one year after the
discovery of their link to narcolepsy. Instead, the authors chose to
focus on the association with various HLA types - a problematic premise
given the discovery of the genetic link to hypocretin/orexin and the
absence of any HLA association in various canine models.
Despite their appropriate word of caution in the discussion that "the
possession of this allele is neither necessary nor sufficient for the
disorder", in the presentation of each case they conclude that the
presence of the HLA types is "consistent with narcolepsy". This is in my
view an overly optimistic statement and may mislead some clinicians to
conclude that HLA typing is a useful diagnosic tool for narcolepsy - which
it is not. Absence of the appropriate HLA type may serve as some evidence
against the disorder, but presence of the allele adds barely any
diagnostic certainty, given the relatively high pre-test probability in
the selected clinic population on whom the HLA typing would be undertaken.
Competing interests: No competing interests