Clinical and Genetic Heterogeneity of Familial Early-Onset Diabetes: Case of Six Tunisian Patients Suspected of Maturity-Onset Diabetes of the Young 12

Background and objective: Maturity-onset diabetes of the young 12 (MODY12) is a form of early-onset type 2 diabetes, which is transmitted in an autosomal dominant mode. It has clinical features similar to MODY1 and MODY3. The aim of this study is to screen for mutations in ABCC8 gene in six Tunisian patients suspected of MODY12 using Sanger sequencing. Methods: Six probands, with diabetes in 2-3 generations and found previously negative for mutations in HNF1A, HNF4A, INS, IPF1 and NEUROD1, were screened for known mutations in ABCC8 gene using Sanger sequencing. A comparison of the clinical features of our patients with MODY12 cohorts of other studies was also performed using ANOVA test. Results: The six patients were diagnosed with overt diabetes (fasting glycemia: 12.85 +/- 3.5 mmol/l, HbA1c: 12.51 +/- 2.58%) at mean age of 25.16 +/- 5.11 years. They had a BMI mean equal to 26.7 +/- 5.9 kg/m(2). The majority of the patients were initially treated with OHA or on diet. Some of them converted to insulin therapy. Although, the comparison of our cohort with other MODY12 cohorts showed no significant difference in age at diagnostic and HbA1c, molecular analysis showed only two synonymous non-pathological polymorphisms rs1799857 and rs1805036. Conclusion: Our study highlighted the clinical and genetic heterogeneity of familial early onset diabetes in the Tunisian population, which is concordant with previous studies Thus, the need for using next generation sequencing technologies to determine the aetiology of these forms of diabetes.