“Aims: we report a complex case of a late-onset patient with a mitochondrial myopathy and a Parkinsonism associated with a mutation in MT-ND3.
Materials and Methods: biochemical tests, electrodiagnostic testing, muscle biopsy, next generation sequencing (NGS), brain and muscle magnetic resonance (MRI), PET-TC total body and DAT-Scan.
Case Description: A 53-year-old male with a history of myocardial infarction due to anti-phospholipid and anti-cardiolipin antibodies, treated with statins and bilateral hypoacusis. He experienced subacute weight loss (approximately 15 kg), myalgia, and limb weakness with elevated CPK, transaminases, and LDH levels. Neurological evaluation revealed involvement of the girdle muscles (slow gait with hyperlordosis and waddling, needing support to rise from squatting) and bulbar muscle involvement (weak pharyngeal reflex and hypophonic voice). The initial suspicion was inflammatory myopathy, leading to extensive negative immunological, infectious, oncological, metabolic, and electrophysiological screening. Muscle MRI indicated proximal muscle fatty degeneration, prompting biopsy revealing mitochondrial impairment (20% ragged-red fibers with reduced COX activity). Further neurological evaluation revealed REM sleep disorder, hyposmia, slowed movements, mild hypertonia, and hypomimic facies. Brain MRI showed bilateral frontotemporal atrophy, and DAT-scan revealed asymmetric hypometabolism in the putamen and caudate. L-dopa treatment led to significant improvement. Given the clinical picture, we tested mitochondrial genes associated with parkinsonism and identified a mutation in MT-ND3 10237I>C.
Discussion and Conclusions: Parkinsonism, although uncommon, can be part of mitochondrial myopathies. Emerging evidence suggests the potential role of mtDNA mutations in parkinsonism. Our case supports this association and contributes to understanding the phenotypic spectrum linked to the rare MT-ND3 mutation.”