Mitochondrial diabetes

Mitochondrial diabetes is a group of rare forms of diabetes caused by mutations of the mitochondrial genome. The commonest form of this diagnosis is due to a mutation in the mitochondrial leucine-transfer RNA gene. They are clinically characterised by maternal transmission, and prevalence is between 0.5% and 2% of all diabetes.

General examination

A thorough general and systems examination is essential in order to detect any complications and to seek signs of other associated conditions, such as cardiomyopathy or neurological abnormality.

What is the patient’s BMI?

Mitochondrial diabetes typically occurs in lean individuals as the defect is one of insulin secretion rather than of insulin resistance. The newly presenting mitochondrial diabetes patient may be mistaken for a case of T1DM without thorough and careful assessment.

What is the BP?

Hypertension is an important risk factor for many complications of diabetes including ischaemic heart disease, cerebrovascular disease, nephropathy and retinopathy.

Retinal screening

As with all newly presenting diabetes, some form of retinal screening should be undertaken, ideally by digital retinal photography as part of an accredited retinal screening programme, but at the very least dilated fundoscopy should be performed by the examining physician.

In newly presenting mitochondrial diabetes this is not just to detect any pre-existing diabetic retinopathy but to assess for the presence of pigmentary retinopathy which can also be associated with mitochondrial genome mutations.

Cardiovascular system

A cardiovascular examination should be performed as a routine part of the new patient assessment in order to detect any unsuspected comorbidities and/or already established complications in all newly presenting cases of diabetes mellitus.

Furthermore, specific signs of cardiomyopathy should be sought in suspected cases of mitochondrial diabetes.

Neurological examination

This should be thorough and particularly look for signs of retinopathy, myopathy, cerebellar ataxia, sensorineural hearing loss and encephalopathy.

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