Variability in the age at diagnosis of diabetes in two unrelated patients with a homozygous glucokinase gene mutation.

Homozygous mutations in the glucokinase gene (GCK) result in a complete deficiency of the GCK enzyme, which leads to permanent neonatal diabetes mellitus. Whilst there has been one report of a patient (with a homozygous p.T168A) who was diagnosed with diabetes at the age of 2 months, all other cases were diagnosed with diabetes within the first 2 weeks of life. We now report a second unrelated patient with the same p.T168A GCK mutation who was diagnosed with diabetes at the age of 9 months. We conclude that the specific GCK mutation, as yet unidentified genetic modifiers, and/or environmental factors might have different effects on pancreatic beta-cell functions, causing variability in the age at diagnosis of diabetes.