The significance of reduced respiratory chain enzyme activities: clinical, biochemical and radiological associations.
BACKGROUND
Mitochondrial diseases are an important group of neurometabolic disorders in children with varied clinical presentations and diagnosis that can be difficult to confirm.


OBJECTIVE
To report the significance of reduced respiratory chain enzyme (RCE) activity in muscle biopsy samples from children.


METHODS
Retrospective odds ratio was used to compare clinical and biochemical features, DNA studies, neuroimaging, and muscle biopsies in 18 children with and 48 without reduced RCE activity.


RESULTS
Children with reduced RCE activity were significantly more likely to have consanguineous parents, to present with acute encephalopathy and lactic acidaemia and/or within the first year of life; to have an axonal neuropathy, CSF lactate >4 mmol/l; and/or to have signal change in the basal ganglia. There were positive associations with a maternal family history of possible mitochondrial cytopathy; a presentation with failure to thrive and lactic acidaemia, ragged red fibres, reduced fibroblast fatty acid oxidation and with an abnormal allopurinol loading test. There was no association with ophthalmic abnormalities, deafness, epilepsy or myopathy.


CONCLUSIONS
The association of these clinical, biochemical and radiological features with reduced RCE activity suggests a possible causative link.
Department of Paediatric Neurology, Sheffield Children's Hospital NHS Trust, Ryegate Children's Centre, Tapton Crescent Road, Sheffield, South Yorkshire S10 2TH, UK. santosh.mordekar@sch.nhs.uk
S R
SR
Mordekar
P
P
Guthrie
J R
JR
Bonham
S E
SE
Olpin
I
I
Hargreaves
P S
PS
Baxter
D000293:Adolescent; D000367:Age Factors; D001921:Brain / Q000473:pathology; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D003241:Consanguinity; D045222:Electron Transport Chain Complex Proteins / Q000378:metabolism*; D005260:Female; D006801:Humans; D007223:Infant; D019344:Lactic Acid / Q000378:metabolism; D008297:Male; D028361:Mitochondrial Diseases / Q000150:complications* / Q000175:diagnosis* / Q000201:enzymology; D009132:Muscles / Q000201:enzymology*
D045222:Electron Transport Chain Complex Proteins; D019344:Lactic Acid