Search for a rare disease

* (*) mandatory field

Other search option(s)

Suggest an update

(*) Required fields.


Only comments seeking to improve the quality and accuracy of information on the Orphanet website are accepted. For all other comments, please send your remarks via contact us. Only comments written in English can be processed.

Orphanet doesn't provide personalised answers. To get in touch with the Orphanet team, please contact

Information provided in your contribution (including your email address) will be stocked in .CSV files that will be sent as an email to Orphanet's teams. These emails might be conserved in the teams' mailboxes, in our backoffice servers but will not be registered in our databases (for more information see our section General Data Protection Regulation and data privacy (GDPR) and Confidentiality).

Captcha image

Idiopathic hypersomnia

Disease definition

A rare neurologic disease characterized by an excessive daytime sleepiness with long and unrefreshing naps, and/or prolonged and undisturbed nocturnal sleep, impaired daytime alertness, and/or sleep inertia (ie, great difficulty in waking up after sleep) and where other causes have been excluded.


Classification level: Disorder
  • Synonym(s):
    • Idiopathic excessive sleepiness
  • Prevalence: 1-5 / 10 000
  • Inheritance: Unknown 
  • Age of onset: All ages
  • ICD-10: F51.1
  • OMIM: -
  • UMLS: C0751757
  • MeSH: -
  • GARD: 8737
  • MedDRA: -

Detailed information


The documents contained in this web site are presented for information purposes only. The material is in no way intended to replace professional medical care by a qualified specialist and should not be used as a basis for diagnosis or treatment.