Definition
When three or more different gene loci influence the expression of a particular condition or trait.
Use in clinical context
Recent studies have shown that some conditions that were considered to be monogenic are not fully explained by variants in a single gene alone, but may be influenced by the effects of other genes. While digenic conditions are caused by two pathogenic gene loci, the term oligogenic is used when three or more gene loci (though typically fewer than 20) influence a particular trait. There is some overlap with the term polygenic, which is used when multiple loci influence a condition.
Due to the involvement of several genes, oligogenic conditions typically have a broad phenotypic spectrum and variable severity. The genes involved may interact in the same cellular pathway, be part of separate pathways (which can contribute to the disease mechanism) or modify the expression of the condition, rather than being directly causative. Environmental factors may also be implicated. Oligogenic inheritance has been associated with several conditions, including breast cancer, Hirschsprung disease, congenital hypogonadotropic hypogonadism and familial hypercholesterolaemia. Further examples of oligogenic conditions and published causative variants can be found in the Oligogenic Diseases Database (OLIDA).
Related terms
Digenic | Gene | Genetic condition | Human Phenotype Ontology | Phenotype | Polygenic | Polygenic condition | Variant
