Given the epidemic of obesity, it is very easy to label every new patient presenting with raised blood glucose as having Type 2 diabetes (T2D). However, even NICE are recognising that other types of diabetes can occur atypically, for example Type 1 diabetes in the middle aged. On top of this, clinicians should be increasingly aware of the possibility that the kneejerk diagnosis of T2DM may be wrong. This is increasingly important given the increasing prevalence in younger patients The presence of a strong family history may indicate a specific subtype of diabetes – MODY (Maturity onset diabetes of the young). Also referred to as monogenic diabetes, the term refers to any of several hereditary forms of diabetes caused by mutations in an autosomal dominant gene. It affects 1-2% of all patients with diabetes and classically presents in patients aged less than 25 years, in families with a multigenerational history of relatively early onset diabetes. Caused by a change in a single gene, 6 genetic subtypes account for 87% cases of MODY in the UK. Diagnosis of a MODY family is of benefit as the natural history of each sub type can determine the long term medication and screening required. Furthermore, family members can be screened in order to predict their longer term risk. The commonest sub type (HNF1A) is responsible for 70% of MODY cases.  A gene mutation results in reduced insulin secretion from the pancreas with diabetes usually occurring in their early 20s. Of note, patients with this subtype of diabetes are usually slim and especially sensitive to sulphonylureas which are the drug of choice, although the condition does progress to requiring other agents including insulin. CVD risk is also raised. The other major subtype, Glucokinase influences the ‘glucose sensor’ within the pancreas resulting in reduced insulin secretion for a given blood glucose and mild chronic hyperglycaemia, typically from birth. Complications are rare and as a result, no specific treatment is required apart from during pregnancy (due to the impact of hyperglycaemia on the foetus). Although clinical suspicion needs to be high, early identification is clearly of benefit both for the patient and family members.

Dr Mark Freeman