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Updated: May 28, 2026

Histological Examination of Mitochondrial Morphology in a Parkinson's Disease Model
Published on: June 23, 2023
Orbicularis oculi: morphological changes mimicking mitochondrial cytopathy in a series of control normal muscles
Penelope McKelvie1, Khami Satchi, Alan A McNab
1Department of Anatomical Pathology, St Vincent's Hospital Melbourne, Fitzroy, VIC 3065, Australia. penny.mckelvie@svhm.org.au
Introduction:
Orbicularis oculi (OO) muscle has recently proposed as a suitable muscle for biopsy to diagnose mitochondrial cyopathy:
Methods:
Enzyme histochemical and immunohistochemical studies were performed on OO muscle obtained from 18 patients aged 37-87 years (median 64 years), 6 males, 12 females, who were undergoing routine upper blepharoplasty surgery.
Results:
We confirmed the marked type II fibre (fast myosin heavy chain) predominance (89%) but also noted a different proportion and distribution of mitochondria in these fibres with occasional pseudo-'ragged-red' fibres with prominent subsarcolemmal and cytoplasmic aggregation of mitochondria. Cytochrome oxidase-negative fibres and true 'ragged-red' fibres were found at all ages over 40 years at levels that approach those used for diagnosis of mitochondrial cytopathy in peripheral or limb skeletal muscles.
Conclusion:
We would therefore urge caution in the use of OO as muscle biopsy for diagnosis of mitochondrial cytopathy and advise concomitant biopsy of limb skeletal muscle and/or supplementary genetic studies.
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