Maternally-inherited diabetes and deafness: report of two affected German families with the A3243G mitochondrial DNA mutation.

In two German families four patients containing the A3243G mutant in the mitochondrial DNA suffered from maternally-inherited diabetes and deafness (MIDD). DNA was isolated from oral mucosa cells. Using the polymerase chain reaction with not yet published primers, we obtained after digestion with the restriction endonuclease BSP 1201 two oligonucleotides of comparable size increasing the sensitivity of our method two times. Under these conditions we were able to detect 0.8% of the mutated DNA. In general, the patients show the characteristics proposed for MIDD by Maassen et al. (1997), however, there are some differences: age at onset (in our study 36-45 y), body mass index (>26 kg/m2). In addition, our study shows that MIDD may be combined with neuronal disorders (M. Parkinson, epilepsy) and/or endocrinopathies (M. Addison). Our data indicate that MIDD is a heterogeneous disease. On the other hand, in one family there are healthy probands with a high concentration of mutated mitochondrial DNA.