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Maternally inherited diabetes and deafness (MIDD)

Maternally Inherited Diabetes and Deafness is a form of genetically inherited diabetes that comprises approximately 1% of all PWD. It is often misdiagnosed as type 1 or type 2 diabetes because it is so rare.

As we all learned in high school cell biology, most of the cell’s DNA exists in the nucleus and chromosomes, but there is a small amount of DNA in the mitochondria known as mitochondrial DNA. Mutations in the mitochondrial DNA are the cause of MIDD and it is maternally inherited because egg cells (not sperm) contribute mitochondria to the developing embryo. Though MIDD can affect both genders, it can only be passed down from the mother.

MIDD is characterized by decreased insulin secretion and sensorineural deafness (particularly in high pitched sounds), both caused by the mitochondrial DNA mutation. Interestingly, the severity of MIDD is thought to be determined by the percentage of mitochondria with the genetic mutation.

Because the cell’s mitochondria are responsible for generating ATP (energy), MIDD most impacts the organs with highly active cells; such as the pancreas and cochlea. But other organ systems can be affected too. Other manifestations of MIDD include...

Short stature and a thin body habitus

Cardiovascular concerns, particularly issues with rhythm

Muscle weakness, generally in proximal muscles

Renal disease

Retinal issues

Strokes in adults <45 years of age

Gastrointestinal issues, especially constipation

Genetic testing should be performed to confirm a diagnosis of MIDD and family testing should be included in the follow up plan.

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