Patients 2 and 4 were initially diagnosed with T2D as they did not require insulin therapy; patient 2 harboring an ABCC8 gene mutation (MODY12) was started on metformin/glibenclamide, while patient 4, with a GCK gene mutation (MODY2), did not receive pharmacological treatment. The gene discussed is ABCC8; the disease is type 2 diabetes mellitus.