Some practical aspects of providing a diagnostic service for respiratory chain defects.
The oxidative phosphorylation system (OXPHOS) is organized into five multi-protein complexes, comprising four complexes (I-IV) of the respiratory chain and ATP synthase (complex V). OXPHOS has a vital role in cellular energy metabolism and ATP production. Enzyme analysis of individual OXPHOS complexes in a skeletal muscle biopsy remains the mainstay of the diagnostic process for patients suspected of mitochondrial cytopathy. Practical guidelines are presented to provide optimal conditions for performance of laboratory investigations and a reliable diagnosis. A fresh muscle biopsy is preferable to a frozen muscle sample because the overall capacity of the OXPHOS system can be measured in a fresh biopsy. In about 25% of patients referred for muscle biopsy to our centre, reduced substrate oxidation rates and ATP+creatine phosphate production rates were found without any defect in complexes I-V and the pyruvate dehydrogenase complex. Investigation of frozen muscle biopsy alone may lead to false-negative diagnoses in many patients. In some patients, it is necessary to investigate fibroblasts for prospective diagnostic purposes. An exact diagnosis of respiratory chain defects is a prerequisite for rational therapy and genetic counselling. Provided guidelines for specimen collection are followed, there are now reliable methods for identifying respiratory chain defects.
Janssen
A J M
AJ
Nijmegen Centre for Mitochondrial Disorders, Department of Pediatrics, University Medical Centre Nijmegen, Geert Grooteplein 10, PO Box 9101, 6500 HB Nijmegen, The Netherlands.
Smeitink
J A M
JA
van den Heuvel
L P
LP
D000255:Adenosine Triphosphate / Q000378:metabolism; D001706:Biopsy; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D028361:Mitochondrial Diseases / Q000175:diagnosis*; D017240:Mitochondrial Myopathies / Q000175:diagnosis*; D008954:Models, Biological; D018482:Muscle, Skeletal / Q000473:pathology; D010085:Oxidative Phosphorylation; D010100:Oxygen / Q000378:metabolism; D011296:Prenatal Diagnosis
D000255:Adenosine Triphosphate; D010100:Oxygen