title: Predictive genetic testing in maturity-onset diabetes of the young (MODY).
abstract: BACKGROUND
  Maturity-onset diabetes of the young (MODY) is characterized by autosomal dominant inheritance of young-onset non-insulin-dependent diabetes. It accounts for approximately 1% of Type 2 diabetes (approximately 20 000 people in the UK). Diagnostic and predictive genetic tests are now possible for 80% of MODY families. Diagnostic tests can be helpful as the diagnosis can be confirmed and the subtype defined which has implications for treatment 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 hepatic nuclear factor (HNF)1alpha 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 counselling. The views of the family and the clinical genetics team involved are presented.
  
  
  RESULTS
  The implications of positive and negative predictive test results and the possibility of postponing the test were among many issues discussed during genetic counselling. The family remained convinced the test was appropriate for their daughter and the clinical genetics team fully supported this decision. The family, motivated by their family history of diabetes and personal experiences of the disease, wished to reduce uncertainty about their daughter's future irrespective of the result.
  
  
  CONCLUSIONS
  This case emphasizes that decisions on predictive testing are very personal and require appropriate counselling.
authors.affiliation: Department of Diabetes and Vascular Medicine, School of Postgraduate Medicine and Health Sciences, University of Exeter, Exeter, UK.
authors.forename: M
authors.initials: M
authors.lastname: Shepherd
authors.forename: I
authors.initials: I
authors.lastname: Ellis
authors.forename: A M
authors.initials: AM
authors.lastname: Ahmad
authors.forename: P J
authors.initials: PJ
authors.lastname: Todd
authors.forename: D
authors.initials: D
authors.lastname: Bowen-Jones
authors.forename: G
authors.initials: G
authors.lastname: Mannion
authors.forename: S
authors.initials: S
authors.lastname: Ellard
authors.forename: A C
authors.initials: AC
authors.lastname: Sparkes
authors.forename: A T
authors.initials: AT
authors.lastname: Hattersley
mesh_terms: D000293:Adolescent; D000328:Adult; D017668:Age of Onset; D001294:Attitude to Health; D002648:Child; D002675:Child, Preschool; D003924:Diabetes Mellitus, Type 2 / Q000453:epidemiology / Q000235:genetics*; D005190:Family / Q000523:psychology; D005260:Female; D005817:Genetic Counseling; D020022:Genetic Predisposition to Disease; D005820:Genetic Testing / Q000523:psychology; D006801:Humans; D015994:Incidence; D008297:Male; D010375:Pedigree; D011237:Predictive Value of Tests; D006113:United Kingdom / Q000453:epidemiology