Orphanet Rare Disease Ontology

 The Orphanet Rare Disease ontology (ORDO) was initially jointly developed by Orphanet and the EBI to provide a structured vocabulary for rare diseases capturing relationships between diseases, genes and other relevant features which will form a useful resource for the computational analysis of rare diseases. It is derived from the Orphanet database www.orpha.net , a multilingual database dedicated to rare diseases populated from literature and validated by international experts. It integrates a nosology (classification of rare diseases), relationships (gene-disease relations, epidemiological data) and connections with other databases (OMIM, MONDO, UniProtKB, HGNC, ensembl, Reactome, IUPHAR, Genatlas) or classifications (ICD-10, ICD-11).

The ontology is maintained by Orphanet.

Orphanet classifications can be browsed in the OLS view. ORDO follows the OBO guidelines on deprecation of terms and is available for download below via the CC-BY-4.0 licence.

ORDO is bi-annually released in July and December.

ORDO release of July 2025

All files are available under the  Commons Attribution 4.0 International (CC BY 4.0) licence

These resources have been recognised as an  Elixir Core Data Resource and a  Global Core Biodata Resource

These resources are an  IRDiRC Recognized Resources