Orphanet maintains the Orphanet nomenclature of rare diseases, essential in improving the visibility of rare diseases in health and research information systems: each disease in Orphanet is attributed a unique and stable identifier, the ORPHA number.
Orphanet uses the European definition of a rare disease, as defined by the European Union Regulation on Orphan Medicinal Products (1999), that being a disease that affects not more than 1 person per 2000 in the European population.
The Orphanet rare disease nomenclature is comprised of a heterogeneous typology of entities of decreasing extension, including: groups of disorders, disorders, sub-types. A disorder in the database can be a disease, a malformation syndrome, a clinical syndrome, a morphological or a biological anomaly or a particular clinical situation (in the course of a disorder). They are organised into groups, and further divided into clinical, etiological or histopathological sub-types.
The ORPHA number for pityriasis rubra pilaris is 2897. The following information is included when searching for ORPHA:2897.
✽ Prevalence: <1 / 1 000 000
✽ Inheritance: Autosomal dominant or Not applicable
✽ Age of onset: Infancy, Neonatal
✽ ICD-10: L44.0
✽ OMIM: 173200
✽ UMLS: C0032027
✽ MeSH: D010916
✽ GARD: 7401
✽ MedDRA: 10035116