Candidate Gene Analyses of Mandibular Prognathism

Causation of a disease and a symptom generally is classified as genetic inheritance and environmental factors. A disease caused by a single gene disorder is defined as a disease that is attributed to a monogenic factor. A single gene disorder has been reported in more than 3,000 hereditary diseases. On the other hand, a polygenic or multifactorial disease is attributed to some susceptibility genes and their interaction with some environmental factors. Mandibular prognathism (Online Mendelian Inheritance in Man (OMIM) #176700), skeletal Class III malocclusion in orthodontics, occurs in populations throughout the world but with a higher incidence in Asian populations. The prevalence is less than 1% in Caucasians while approximately 10% in Japanese. Mandibular prognathism has been caused by various patterns of genetic inheritance and/or environmental factors in previous studies. In the 20th century, multiple models of inheritance of mandibular prognathism, including monogenic inheritance, autosomal-dominant inheritance, autosomal-recessive inheritance, and polygenic inheritance, have been suggested. A family line of Habsburg, the Spanish and Austrian Royal family, shows an autosomal-dominant inheritance based on multiple generations. However, now it is evident that the majority of mandibular prognathism is a multifactorial phenotype [1,2].