Diabetes caused by mutations in the glucokinase (GCK) gene. This gene contains the blueprint for an enzyme that is important for the normal regulation of insulin production. MODY 2 is one of the most common types of MODY.
Image source: Fajans SS, Bell GI, Polonsky KS. “Molecular mechanisms and clinical pathophysiology of maturity-onset diabetes of the young.” N Engl J Med. 2001 Sep 27;345(13):971-80.
Presentation:
MODY 2 typically results in mildly elevated fasting blood sugar in the morning. These elevated morning blood sugars are usually picked up incidentally by health care providers. MODY 2 does not usually manifest with symptoms associated with very high blood sugars. Mutations can occur spontaneously but usually are passed on from a parent to a child. If a parent has MODY 2 there is a 50% chance that a child will inherit the mutation and be at risk of developing diabetes at a young age.
In adults, distinguishing MODY 2 from early type 2 diabetes can be difficult. Features that make us suspect MODY 2 include
- Fasting sugars of 100-140mg/dl (5.6- 7.5mmol/l) for many years
- 2 or 3 generations of diabetes diagnosed at a young age
- A HbA1c that does not go over 7.8%
- Blood sugars rarely ever go above 250mg/dl (14mmol/l)
In children, MODY 2 can be misdiagnosed as early type 1 diabetes.
In this setting some additional features make us suspect MODY 2 include
- Negative antibody testing
- Persistently detectable C-Peptide
- No history of diabetic ketoacidosis
Treatment:
Treatment for MODY 2 is rarely indicated if the mildly raise blood sugars remain stable. Often this means that the fasting glucose and HbA1c results are slightly higher than the target treatment goals for type 1 and type 2 diabetes.
Women with MODY may require treatment during pregnancy. If you or a family member become pregnant and have MODY 2 then please don’t hesitate to contact us.
Inheritance:
Finding a GCK mutation in a patient’s family may have implications for other family members- who may be carriers as well. An affected person’s child will each be at a 50% risk of inheriting the mutation and developing diabetes
Research:
If you or a family member have MODY 2 or suspect yourself or a family member of having MODY 2 then please contact us to learn more about our studies.
