Adolescent non-adherence reveals a genetic cause for diabetes

Abstract

Background: Glucokinase related maturity-onset diabetes of the young (GCK-MODY) is a form of monogenic diabetes characterized by mildly elevated fasting blood sugars and HbA(1c) typically ranging from 38 to 60 mmol/mol (5.6-7.6%). It is frequently unrecognized or misdiagnosed as Type 1 or Type 2 diabetes, resulting in unnecessary pharmacologic therapy.

Case report: Two brothers were initially diagnosed with Type 1 diabetes mellitus. The brothers were maintained on a total daily insulin dose of 0.3-0.5 units/kg/day and had HbA(1c) values of 40-51 mmol/mol (5.8-6.8%) throughout childhood. After over 10 years of insulin treatment, the younger brother chose to discontinue his insulin therapy without informing his family or his clinician. Following cessation of insulin treatment, he did not experience any change in overall glycaemic control. Subsequent research-based genetic testing revealed a deleterious mutation in GCK in both brothers (p.Val182Met). The older brother subsequently discontinued insulin therapy and both have remained off all pharmacological therapy with good glycaemic control (HbA(1c) < 53 mmol/mol, < 7%) and no adverse complications. The family was advised to seek confirmatory genetic testing in the father and other relatives with hyperglycaemia.

Conclusion: The family described above exemplifies the rationale behind considering a genetic cause when evaluating every person with new-onset hyperglycaemia or those with atypical diabetes. The cost of genetic testing for the most common MODY causing genes may be offset by savings made in therapeutic costs. It is important that all clinicians supervising diabetes care recognize the cardinal features that distinguish GCK-MODY from other forms of diabetes.