Clinical and genetic characterization and long-term evaluation of individuals with maturity-onset diabetes of the young (MODY): The journey towards appropriate treatment.

Aims: To describe the clinical and genetic characteristics and long-term follow-up of a cohort with maturity-onset diabetes of the young (MODY), and to evaluate how molecular diagnosis impacted on treatment.

Methods: A large observational, retrospective, cohort study included individuals referred to the University of São Paulo's Monogenic Diabetes Unit between 2011 and 2020. Comprehensive clinical and genetic evaluations were performed.

Results: Overall, 228 individuals (190 GCK-MODY and 38 HNF1A-MODY) were enrolled. Sixty-two different GCK gene mutations (5 novel) and 17 HNF1A gene mutations (2 novel) were found. Data were available on treatment status for 76 index individuals with GCK-MODY. Before molecular diagnosis, nutritional intervention alone was used in 41 cases (53.9%). After molecular diagnosis, this number increased to 72 (94.8%). Glycated haemoglobin (HbA) remained stable over the 6-year follow-up period: 6.5% (47 mmol/mol) at the first and 6.3% (45 mmol/mol) at the final visit (p = 0.056). Prior to molecular diagnosis, 7/21 (33.3%) HNF1A-MODY individuals were using sulfonylurea compared to 17/21 (81%) after testing. After a median of 5 years on sulfonylureas, HbA values improved from 7.5% (58 mmol/mol) to 6.5% (48 mmol/mol) (p = 0.006).

Conclusions: Molecular diagnosis resulted in appropriate adjustment of treatment in approximately 80% of participants with GCK-MODY or HNF1A-MODY.