Genetic testing in maturity onset diabetes of the young (MODY): a new challenge for the diabetic clinic

The identification of five genes that can cause maturity onset diabetes of the young (MODY) means diagnostic and predictive genetic testing is now possible in 80% of MODY families. It is proposed that these recent classifications of diabetes ‘genetic disorders of beta cell function’ are recognised as separate disorders. Diagnostic genetic tests in those with diabetes will define the subtype, which has specific implications for treatment. In non‐diabetic family members predictive tests can be used to test whether the mutated gene has been inherited, indicating >90% chance of developing diabetes. This article reviews the genetics of MODY and experiences of genetic testing in diabetes to date and considers what can be learnt from genetic testing in other diseases. Experience from MODY and other conditions suggests that personal perception of the illness and lay beliefs about inheritance are important. Discussion of priorities within genetic counselling and motivation for testing are also crucial when communicating genetic information. Understanding perceptions of genetic information in diabetes and the implications of genetic testing in MODY is a challenge for the 21st century. This will provide insights into how to communicate effectively about genetic testing in diabetes. Genetic testing will be more widely used in the near future as the technology for testing becomes cheaper and easier and other monogenic subtypes of type 2 diabetes are defined.