Clinical Signs and Symptoms

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Orphanet provides a clinical description of rare diseases using a set of clinical signs and symptoms (phenotypic abnormalities).

This description, based on cases published in biomedical literature, uses the phenotypic abnormalities referenced in the Human Phenotype Ontology (HPO).

Each phenotypic abnormalities are presented by order of frequency of occurrence in the patient population :

The frequency in the patients' population can be :

  • - always present: 100%
  • - very frequent: 99%-80%
  • - frequent: 79%-30%
  • - occasional: 29%-5%
  • - rare: 4%-1%

The phenotypic abnormality can be defined as one of the following :

  • - Pathognomonic sign : a sign whose presence indicates that a particular disease is present beyond any doubt. The absence of this sign does not exclude the possibility of the presence of the disease, but the presence of the pathognomonic sign affirms it with certainty.
  • - Diagnostic criterion : phenotypic abnormalities noted as « diagnostic criterion » are those included in established sets of criteria to establish the diagnosis of a particular disease having been published in a peer-reviewed journal.
  • - Exclusion criterion : phenotypic abnormalities noted as « exclusion criterion » are those that are always absent in a particular disease and therefore exclude its diagnosis.


The information provided is based on published scientific articles.

The information provided is estimated for the entire population of patients in routine care. Some phenotypic abnormalities reported here may occur individually with a variable temporality or severity, while others, not listed, may still be encountered. Phenotypic annotations are not yet available for all rare diseases; the annotation process is ongoing.

The information contained in Orphanet is regularly updated. It is possible that discoveries have been made since the last update and have not yet been incorporated.

Professionals are encouraged to always consult the latest scientific publications before making a decision based on the information provided. The information contained in Orphanet is not intended to replace the services of a healthcare professional. Orphanet cannot be held responsible for the deleterious, truncated or erroneous use of any information found in the Orphanet database.