Clinical Question
Can we reduce delays in correctly assigning a diagnosis of monogenic diabetes?
INTRODUCTION
A GP will often be the first health professional involved in making a diagnosis of diabetes. For adults who do not need immediate insulin treatment, a default diagnosis of type 2 diabetes is the most common outcome, but a small proportion of patients will actually have maturity-onset diabetes of the young (MODY; a type of monogenic diabetes).
MODY is inherited in an autosomal dominant pattern and estimated to account for 1–2% of all diabetes.1 MODY is most commonly caused by mutations in genes encoding the transcription factors HNF1A, HNF4A, and HNF1B, and the glycolytic enzyme glucokinase (GCK).1
Making a correct molecular diagnosis is crucial, as this allows optimal treatment and therefore the best long-term outcome. It is estimated that around 80% of MODY patients are misdiagnosed as type 1 (T1DM) or type 2 diabetes (T2DM),1 and a delay of >10 years from presentation of diabetes to molecular diagnosis is frequently reported.2 Two cases where genetic referral for MODY was arranged at presentation of diabetes are described.
CASE PRESENTATIONS
Case 1
An 18-year-old female presented to her GP with 2 kg weight loss, mild polydipsia, and polyuria but otherwise well. Her fasting blood glucose of 12 mmol/L was diagnostic of diabetes (normal range 3.9–5.5 mmol/L). Her mother had been diagnosed with T1DM at age 15 years and treated with insulin. Her paternal grandfather had diabetes diagnosed in his forties and was treated successfully with an oral agent for four decades.
Referral to the monogenic diabetes clinic was made for investigation. Her BMI was 17 kg/m2 with no signs of …