A review of maturity onset diabetes of the young (MODY) and challenges in the management of glucokinase-MODY

Summary

• Maturity onset diabetes of the young (MODY), the most common monogenic form of diabetes, accounts for 1–2% of all diabetes diagnoses.
• Glucokinase (GCK)-MODY (also referred to as MODY2) constitutes 10–60% of all MODY cases and is inherited as an autosomal dominant heterozygous mutation, resulting in loss of function of the GCK gene.
• Patients with GCK-MODY generally have mild, fasting hyperglycaemia that is present from birth, are commonly leaner and diagnosed at a younger age than patients with type 2 diabetes, and rarely develop complications from diabetes. Hence, treatment is usually unnecessary and may be ceased. Therefore, genetic screening is recommended in all young patients (< 40 years) with an autosomal dominant family history of diabetes and who lack features of the metabolic syndrome and type 1 diabetes. Further, treatment discontinuation should be discussed with the patient as part of the informed consent process, as the realisation that prior treatment may have not been necessary — or that it could have been less burdensome — may have psychological implications for the patient. This is true for other forms of MODY, such as hepatocyte nuclear factor 1A mutations (MODY3) where hyperglycaemia is managed with low dose sulfonylurea rather than insulin.
• Patients with GCK-MODY, in line with trends in the general population, are becoming older and more overweight and obese, and are concomitantly developing features of insulin resistance and glucose intolerance. Therefore, controversy exists as to whether such “treatment-exempt” patients should be reassessed for treatment later in life.
• As testing becomes more accessible, clinicians and patients are likely to embrace genetic screening earlier in the course of diabetes, which may avert the consequences of delayed testing years after diagnosis and treatment initiation.