Patients with type 2 diabetes have a high frequency of the C282Y mutation of the hemochromatosis gene.

OBJECTIVE: To determine whether a specific mutation (C282Y) associated with primary hemochromatosis (PHC) is more common in patients with type 2 diabetes than in a control group of patients with type 1 diabetes. Patients with type 2 diabetes have a two- to threefold higher rate of PHC than the general population. Recent identification of a genetic mutation in patients with PHC raises the possibility that the mutation is related to type 2 diabetes. DESIGN: Cross-sectional study. SUBJECTS: One hundred and five patients with type 2 diabetes and 103 control patients with type 1 diabetes, who attended the same tertiary care diabetes clinic, who were of European origin, and in whom there was no clinical suspicion of hemochromatosis. INTERVENTIONS: Patients completed a brief clinical assessment and provided a blood sample. Iron studies were measured in serum, and DNA was assayed for the presence of the C282Y and H63D mutations of the HFE gene. RESULTS: Twenty-three of 105 patients (21.9%, 95% confidence interval [CI] 14.0, 29.8) with type 2 diabetes (1 homozygote) and 12 of 103 patients (11.7%; 95% CI 5.5, 17.9) with type 1 diabetes (all heterozygotes) had at least 1 copy of the C282Y mutation (odds ratio [OR] = 2.1; 95% CI 1.0, 4.5; p = 0.048). Neither serum ferritin nor transferrin saturation level identified patients with a C282Y mutation. CONCLUSION: The C282Y gene mutation is a potential genetic marker for type 2 diabetes. It, or a closely linked gene, may be associated with greater than 20% of cases of type 2 diabetes.