Maturity-onset diabetes of the young (MODY) is the most common form of monogenic diabetes and affects 1% to 2% of people with diabetes.
MODY is caused by mutation of a single gene (i.e., monogenic). It has autosomal dominant inheritance and should be suspected in cases of diabetes in non-obese, young patients (adolescence or young adult) with family history of diabetes in two or more successive generations.
Presents with non-ketotic, non-insulin-dependent diabetes that responds to oral glucose lowering drugs.
Genetic testing in patients with high index of suspicion identifies mutations most commonly in genes encoding glucokinase and transcription factors.
Diabetes diagnosed under 6 months of age.
Usually isolated diabetes in an autosomal dominant pattern of inheritance.
Some monogenic causes are characterised by a variety of syndromic features.
Genetic testing with majority of mutations in the genes encoding the adenosine triphosphate-sensitive potassium channel and the insulin gene.
Typical age of onset of diabetes is over 30 years old. Patients are usually non-obese and respond initially to lifestyle modifications and oral agents. Production of insulin gradually decreases (between 6 months and 5 years), such that treatment with insulin is required.
LADA is considered a subset of type 1 diabetes; however, patients with LADA are frequently misclassified as having type 2 diabetes.
Low to normal initial C-peptide level.
Can be positive for at least 1 of the 4 antibodies commonly found in type 1 diabetic patients.
Typically, signs of insulin resistance (such as acanthosis nigricans) should be sought and in their absence clinical suspicion of type 1 diabetes is greater.
Signs of more marked insulin deficiency (for example, glycaemic lability as well as susceptibility to ketosis) raise suspicion of type 1 diabetes.
Older age and slow onset, obesity, a strong family history, absence of ketoacidosis, and initial response to oral anti-hyperglycaemic drugs are typical of type 2 diabetes.
Testing for C-peptide and autoantibodies usually not required.
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