Orphanet: Hypernychthemeral syndrome

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Non-24-hour sleep-wake syndrome

Disease definition

Non-24-hour sleep-wake disorder (non-24 disorder), also known as hypernychthemeral syndrome, is a circadian rhythm sleep disorder characterized by non-synchronization to a 24-hour day leading to insomnia and daytime sleepiness with sometimes severe associated manifestations.


Classification level: Disorder
  • Synonym(s):
    • Hypernychthemeral syndrome
  • Prevalence: Unknown
  • Inheritance: Unknown 
  • Age of onset: All ages
  • ICD-10: G47.2
  • OMIM: -
  • UMLS: C0751759
  • MeSH: -
  • GARD: 10949
  • MedDRA: -
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