Nomenclature and classification of rare diseases

Orphanet maintains the Orphanet nomenclature of rare diseases, a unique and multilingual standardised system aimed at providing a specific terminology for rare diseases, essential in improving rare disease visibility in health and research information systems.
Each disease is attributed a unique and stable identifier, the ORPHAcode. The nomenclature is organised in a multi-hierarchical and polyparental classification, structured by medical specialty according to diagnostic and therapeutic relevance. Each clinical entity is attributed one classification level (Group of disorders, Disorder, or Subtype of disorder), and is included in as many medical specialties as necessary according to its clinical presentation.
We provide several datasets extracted from the Orphanet database that facilitate the exploitation of various rare disease -related datasets offered by Orphanet:

Orphanet nomenclature files for coding
(updated annually)

Orphanet nomenclature files for coding (updated annually) designed to allow the implementation of the Orphanet nomenclature in Health Information Systems. The dataset includes all Orphanet clinical entities, their alignments with ICD-10 codes, and the Orphanet classification.
Available in English, French, German, Dutch, Italian, Spanish, Portuguese, Polish and Czech.

Orphanet nomenclature and alignment with terminologies and databases
(updated monthly)

Orphanet nomenclature and alignment with terminologies and databases (updated monthly): this dataset includes all Orphanet clinical entities and their alignments with external terminologies or resources (ICD-10, OMIM, UMLS, MeSH, MedDRA and GARD). The alignments specify the comparability between terminologies by defining if the concepts are perfectly equivalent (exact mapping) or not.
Available in English, French, German, Dutch, Italian, Spanish, Portuguese, Polish and Czech.

Classification of rare diseases
(updated monthly)

a list of datasets, each one listing all rare diseases classified in one of the medical specialties by which the Orphanet classification is organised.
Available in English.

Linearisation of rare diseases
(updated monthly)

this dataset includes all rare diseases present in the Orphanet nomenclature each attributed to one preferred medical specialty.
Available in English.




Video tutorials


What is the Orphanet nomenclature of rare diseases?




Frequently Asked Questions



Free access products description


Orphanet procedures


Orphanet nomenclature and classification of rare diseases


ICD-10 coding rules for rare diseases


Naming rules for the rare disease nomenclature in English


Nomenclature production in national language


Linearisation rules for Orphanet classifications


Orphanet Standard Operating Procedures