Human Phenotype Ontology and SNOMED CT
Human Phenotype Ontology (HPO)
The HPO is owned and released by the Monarch Initiative (https://hpo.jax.org/), for the description of clinical terms relating to phenotypes. As of December 2025 it contains 18,689 terms that document these variations, with a wide range of content and an example of which are those which relate to the bones of the limbs (2,400 terms) and in particular the hands and feet. These HPO codes may be associated with specific genetic changes, which then gives the opportunity of building a complete genetic profile for individual patients.
How many fingers are there ? -
Polydactyly is an example of one of the many deformities of the hands and feet covered by HPO, which are caused by gene mutations, which may be inherited or spontaneous.
How many thumbs are there ?
The x-ray above shows a supernumerary thumb, which is defined as an additional digit on the radial side of the hand. For a complete list (subset) of thumb morphologies see the download page (Mapping files for download) .
Links to other pages
Post-coordinated expressions - the process
Graham Ponting - Independent Clinical Terminologist
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