An autosomal genetic disease that is characterized by the presence of two mutated copies of the gene, both of which must be present in order for the disease or trait to develop. [ http://purl.obolibrary.org/obo/ECO_0007637 http://purl.obolibrary.org/obo/ECO_0007640 url:http://www.nlm.nih.gov/medlineplus/ency/article/002052.htm url:http://ghr.nlm.nih.gov/handbook/inheritance/inheritancepatterns ]