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.

Baseline FBC and biochemical profile

FBC, U+Es, LFTs and lipid profile should be obtained in all cases as part of thorough baseline assessment of the patient and also to detect other associated conditions such as nephropathy.

Lactate

Given the association of mitochondrial mutations with lactic acidosis-prone states, recording a baseline lactate level is part of thorough work up of these cases.

OGTT

An OGTT is not necessary if the patient’s fasting glucose is greater than 7 mmol/L, or the random is greater than 11 mmol/L in a symptomatic patient on a single occasion or twice in an asymptomatic patient.

Otherwise a standard 75 g two hour OGTT should be performed after an overnight fast.

HbA1c

This is a useful baseline but at present is not a diagnostic criteria.

ECG

This should be performed to both detect pre-existing ischaemic heart disease and to look for conduction abnormalities, which can be seen in mitochondrial-associated cardiomyopathies.

Auto antibodies

Islet cell antibodies and anti-gad antibodies should only be tested if there is any doubt as to whether the patient actually has T1DM.

C-peptide levels

These should only be tested if there is doubt as to whether the patient actually has T1DM.

Genetic analysis

Molecular confirmation of the diagnosis by genetic analysis of the mitochondrial genome should be performed.

Although it is expensive it gives the patient and physician absolute confidence that the diagnosis is correct and has important implications for genetic counselling of other affected family members.

Audiology

If the patient has not had their hearing loss formally assessed they should be referred for a full audiological work-up.

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