Complications of Diabetes and Deafness Inherited through the Patient's Mother

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The summary below is from the full report titled "Maternally Inherited Diabetes and Deafness: A Multicenter Study." It is in the 1 May 2001 issue of Annals of Internal Medicine (volume 134, pages 721-728). The authors are PJ Guillausseau, P Massin, D Dubois-LaForgue, J Timsit, M Virally, H Gin, E Bertin, JF Blickle, B Bouhanick, J Cahen, S Caillat-Zucman, G Charpentier, P Chedin, C Derrien, PH Ducluzeau, A Grimaldi, B Guerci, E Kaloustian, A Murat, F Olivier, M Paques, V Paquis-Flucklinger, B Porokhov, J Samuel-Lajeunesse, and B Vialettes.

What is the problem and what is known about it so far?

Diabetes is a disease characterized by persistent elevations in blood sugar levels, which can lead to damage of the eyes, heart, kidneys, and nerves. A few people with diabetes (fewer than 3%) inherit it from their mothers, along with hearing loss or deafness. This rare type of diabetes, known as maternally inherited diabetes and deafness (MIDD), may be caused by specific genetic defects in the mechanisms that normally produce energy for the body. Information about MIDD has been scant because few people have this type of diabetes, and we are just beginning to understand how to study genetic defects of this kind.

Why did the researchers do this particular study?

The researchers wanted to describe complications that are experienced by people with MIDD.

Who was studied?

The study included 54 men and women with MIDD from several sites in France. All participants had known genetic defects in their energy-producing mechanisms.

How was the study done?

The researchers asked standard questions about patients' medical histories and onset of diabetes. They gave participants physical examinations and laboratory tests to see whether the diabetes had affected the patients' eyes, hearts, kidneys, and muscles.

What did the researchers find?

The average age at which diabetes had been diagnosed was 38 years; half of the patients received the diagnoses before age 35. None of the patients were obese. Twenty-nine of the 54 patients had known maternal family histories of diabetes, and all but one had hearing loss in both ears. Forty-two patients had a particular abnormality in the retina (the light-sensitive tissue in the eye). This problem, known as macular pattern dystrophy, showed up as colored spots or scars on eye examination, but only six patients had problems with vision. Twenty-two patients had painful muscle weakness, and 13 had problems with protein (albumin) escaping into the urine through their kidneys.

What were the limitations of the study?

The study was small. People were examined only once, and they had had MIDD for varying lengths of time. The role of treatment in preventing complications was not evaluated.

What are the implications of the study?

A diagnosis of MIDD should be considered in diabetic patients who have the following characteristics: relatively young age at onset, normal or low body weight, deafness, and characteristic eye findings known as macular pattern dystrophy.