Dr. Allison Edgecombe
Resident PGY4
Case One
Overview
Clinical history: This 54-year old female has a past medical history significant for bilateral progressive ptosis, dysphagia and ataxia. Physical examination revealed bilateral temporalis muscle wasting and facial weakness. Horizontal, upward and downward gaze were all significantly restricted. Upper and lower extremity strength and reflexes were unremarkable. The electrophysiologic tests were abnormal and consistent with a clinical diagnosis of a myopathy involving facial muscles. A quadriceps muscle biopsy was performed.
What is the most probable diagnosis?
Diagnosis
Diagnosis: Mitochondrial Myopathy.
There are rare scattered fibres with granular basophilic staining on haematoxylin and eosin stained sections. The modified Gomori trichrome stain and NADH stain highlights theses fibres as ragged red fibres. Cytochrome oxidase staining shows abundant cytochrome oxidase-negative fibres. Electron microscopy (EM) identifies several typical intramitochondrial paracrystalline (parking lot) inclusions.
Mitochondrial myopathies usually present before age 20 with a variety of clinical manifestations including muscle weakness, external ophthalmoplegia, ptosis, hearing loss, cerebral infarction, seizures, dementia or cardiomyopathy. A number of specific disease entities have been described. Mutations in mitochondrial DNA or nuclear DNA encoding mitochondrial genes are identified. Characteristic muscle biopsy findings are ragged red fibres, cytochrome oxidase negative fibres and EM paracrystalline mitochondrial inclusions.
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