GCK-MODY (MODY 2)

Diabetes caused by mutations in the glucokinase (GCK) gene. This gene contains the blueprint for an enzyme that is important in for the normal regulation of insulin production. MODY 2 is one of the most common types of MODY.

gck-mody-gene

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 manifests 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.

Treatment for women with MODY during pregnancy may require treatment. 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.