Diagnosis and Management of Monogenic Diabetes

Characteristics of MODY Subtypes

The American Diabetes Association notes that GCK-MODY (MODY2) is the most frequent subtype, characterized by mild, stable, and non-progressive fasting hyperglycemia 1, 2
HNF1A-MODY (MODY3) is the second most common subtype, presenting with progressive insulin secretory defect, typically appearing in adolescence or early adulthood 1, 3
HNF4A-MODY (MODY1) is the third most common subtype, also with progressive insulin secretory defect 1, 2
HNF1B-MODY (MODY5) is less frequent and associated with renal disease, genitourinary anomalies, and pancreatic atrophy 1, 3

GCK-MODY (MODY2) presents with a higher glucose threshold for insulin secretion, stable and non-progressive fasting hyperglycemia, and rarely requires treatment except during pregnancy 1, 2
HNF1A-MODY (MODY3) is sensitive to sulfonylureas, which are considered first-line therapy, and may require insulin over time 1, 2, 4
HNF4A-MODY (MODY1) is also sensitive to sulfonylureas and may present with high birth weight and transient neonatal hypoglycemia 1

Accurate diagnosis has significant implications for treatment and justifies genetic testing 1, 5, 6
Genetic testing is becoming increasingly cost-effective and often covered by medical insurance 6
Diagnosis can lead to the identification of other affected family members 6

Diabetes diagnosed at a young age (classically before 25 years) 1, 5
Family history of diabetes in successive generations, indicating an autosomal dominant inheritance pattern 5
Atypical presentation of diabetes, with clinical characteristics not typical of type 1 or type 2 diabetes 5
Absence of autoantibodies associated with diabetes 6
Absence of obesity and other characteristics of the metabolic syndrome 6
Stable and mild fasting hyperglycemia (100-150 mg/dL) and HbA1c between 5.6% and 7.6% 6