Predictive genetic testing in maturity-onset diabetes of the young (MODY)

Introduction Maturity-onset diabetes of the young (MODY) is characterized b y autosomal dominant inheritance of young-onset non-insulin-dependent diabe tes. It accounts for approximately 1% of Type 2 diabetes (approximately 20 000 people in the UK). Diagnostic and predictive genetic tests are now poss ible for 80% of MODY families. Diagnostic tests can be helpful as the diagn osis can be confirmed and the subtype defined which has implications for tr eatment and prognosis. However predictive genetic testing, particularly in children, raises many scientific, ethical and practical questions. Methods This is a case report of a family with diabetes resulting from an h epatic nuclear factor (HNF)1 alpha mutation, who request a predictive test in their 5-year-old daughter. The scientific issues arising from molecular genetic testing in MODY are discussed, along with the process of genetic co unselling. The views of the family and the clinical genetics team involved are presented. Results The implications of positive and negative predictive test results a nd the possibility of postponing the test were among many issues discussed during genetic counselling. The family remained convinced the test was appr opriate for their daughter and the clinical genetics team fully supported t his decision. The family, motivated by their family history of diabetes and personal experiences of the disease, wished to reduce uncertainty about th eir daughter's future irrespective of the result. Conclusions This case emphasizes that decisions on predictive testing are v ery personal and require appropriate counselling.