Maternally inherited diabetes and deafness (MIDD): diagnosis and management

Maternally inherited diabetes with deafness is rare diabetes caused by a mitochondrial DNA defect. 85% of cases are associated with m.3243A>G mutation. It is important to diagnose this form of diabetes because of the unique management issues and associated comorbidities. A very strong family history of diabetes, deafness and presence of retinal dystrophy should prompt an investigation for MIDD. Microvascular complications out of keeping with duration of diabetes are another clue to the diagnosis. Retinal and renal manifestations of mitochondrial disease may be confused for diabetic complications. Glutamic acid decarboxylase (GAD) autoantibody negativity in a nonobese diabetic is another clue. Cardiac conduction defects and GDM may also raise suspicion as to the diagnosis. Recognizing this etiology of DM should promote family screening, genetic counseling, screening of associated comorbidities, avoidance of metformin, and cautious use of statins. We report a 77 years old lady with MIDD who was being followed up as insulin requiring type 2 diabetes. We then identified 5 more patients with MIDD in the same clinic. They all had A3243 mutation with characteristic clinical presentation. The pharmacological approaches discussed in the paper are unlikely to work in these patients as they were diagnosed late.