Type 1 diabetes mellitus (DM) is a frequent complication in patients with beta-thalassemia. It is believed to be due to the damage inflicted by iron overload of the pancreatic beta cells.

Liver disorders and genetic influences seem to be additional predisposing factors.

Objective: To study the prevalence of diabetes and impaired glucose tolerance (IGT) in transfusion-dependent Egyptian beta-thalassemic patients and to evaluate the possible role of genotyping in the pathogenesis of diabetes associated with beta-thalassemia. Research design and methods: A total of 56 transfusion-dependent beta-thalassemic patients aged 10-31 (mean age = 15.9 +/- 5.7 yr), 32 males and 24 females, including 48 thalassemia major and eight thalassemia intermedia; compared to 15 age- and sex-matched controls. All were subjected to history and examination, laboratory investigations: complete blood count (CBC), serum ferritin, liver function tests, hepatitis B and C markers, fasting blood glucose, oral glucose tolerance test (OGTT) and fasting C-peptide. Genotyping for 16 mutations was assessed in thalassemic patients with abnormal glucose tolerance.

Results: The prevalence of diabetes was 10.4% (5 of 48) and IGT was 14.6% (7 of 48) among thalassemia major, whereas, none of thalassemia intermedia had abnormal glucose tolerance. Fasting C-peptide was lower in beta-thalassemic patients compared to controls (p < 0.001); the level was significantly higher in patients complicated by diabetes or IGT compared with other thalassemic patients (p < 0.001). Chronic hepatitis C was detected in all patients (100%) with abnormal glucose tolerance. Genotyping showed that IVS II nt 745 was detected in 77.7% of cases with abnormal glucose tolerance.

Conclusions: Abnormal glucose tolerance is common in multiply transfused beta-thalassemia major patients, which could be attributed to progressive and early loss of beta-cell mass, along with persistent insulin resistance. Chronic hepatitis C may play a role in the development of abnormal glucose tolerance.

An association between diabetes and genotyping IVS II nt 745 was found. Patients with this particular genotype are advised to check their blood glucose every 6 months to detect early occurrence of diabetes.