Added the following:
MODY forms of diabetes were long believed to affect around 2% of all people diagnosed with both type 1 and type 2 diabetes. However, a study of 586 children diagnosed with Type 1 diabetes found that a full 8% of them were actually carrying one of the three most common MODY genes. It is likely that a similar number of people diagnosed with Type 2 may also have one of these genetic forms of diabetes, too.
Prevalence, Characteristics and Clinical Diagnosis of Maturity Onset Diabetes of the Young Due to Mutations in HNF1A, HNF4A, and Glucokinase: Results From the SEARCH for Diabetes in Youth. Catherine Pihoker et al.J Clin End & Metab October 1, 2013 vol. 98 no. 10 4055-4062.
Also further down the page in the list of Signs You Don't Have MODY: