RT Journal Article SR Electronic T1 Two siblings with a rare type of maturity-onset diabetes of the young (MODY) JF BMJ Case Reports JO BMJ Case Reports FD BMJ Publishing Group Ltd SP e249362 DO 10.1136/bcr-2022-249362 VO 16 IS 2 A1 Alhakim, Fatima Riyadh A1 AlKhayyat, Haya YR 2023 UL http://casereports.bmj.com/content/16/2/e249362.abstract AB Maturity-onset diabetes of the young (MODY) is a type of diabetes that does not entirely fit the usually encountered type 1 or type 2 diabetes. It is a monogenic, familial and non-autoimmune diabetes among children and young adults resulting from autosomal dominant gene mutations.MODY diagnosis is confirmed by molecular genetic testing, which is costly. Therefore, it is rarely done.Nearly 1%–6% of diabetes has a monogenic cause but this is frequently misclassified as type 1 diabetes mellitus due to the lack of genetic testing. Therefore, a correct diagnosis of MODY is crucial for determining the plan of management. Furthermore, having a patient with MODY in a family indicates screening other family members. In this case report, we highlight that paediatric diabetes cases are not always type 1 or type 2 diabetes mellitus since two siblings incidentally presented with hyperglycaemia and a confirmed diagnosis of MODY type 10 was ultimately made. Moreover, their mother who was previously labelled as a case of type 1 diabetes mellitus was diagnosed later as MODY after genetic testing.