The Usefulness of Muscle Biopsy in Initial Diagnostic Evaluation of Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke-Like Episodes

Elderly onset of MELAS in a male: A case report

BACKGROUND

Mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes (MELAS) is one of the most common maternally inherited mitochondrial diseases which rarely affects elderly people.

CASE PRESENTATION

We reported the case of a 61-year-old male patient with MELAS. He was experiencing acute migraine-like headaches as the first symptoms. Laboratory data showed elevated lactate and creatine kinase levels. Brain magnetic resonance imaging (MRI) found a high signal intensity lesion in the left occipital-temporal-parietal lobe on diffusion-weighted imaging (DWI). Magnetic resonance angiography (MRA) revealed reversible vasoconstriction of the middle cerebral arteries and superficial temporal arteries. A muscle biopsy suggested minor muscle damage. A genetic study revealed a mitochondrial DNA A3243G mutation.

CONCLUSION

Elderly onset of MELAS is rare and easily misdiagnosed as an ischemic stroke. MELAS with the onset of stroke-like episodes should be considered in adult or elderly patients with imaging findings that are atypical for cerebral infarction. The use of multimodal MRI in the clinical diagnosis of MELAS could be extremely beneficial.

Clinical Characteristics of Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke-Like Episodes

Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome, a maternally inherited mitochondrial disorder, is characterized by its genetic, biochemical and clinical complexity. The most common mutation associated with MELAS syndrome is the mtDNA A3243G mutation in the MT-TL1 gene encoding the mitochondrial tRNA-leu(UUR), which results in impaired mitochondrial translation and protein synthesis involving the mitochondrial electron transport chain complex subunits, leading to impaired mitochondrial energy production. Angiopathy, either alone or in combination with nitric oxide (NO) deficiency, further contributes to multi-organ involvement in MELAS syndrome. Management for MELAS syndrome is amostly symptomatic multidisciplinary approach. In this article, we review the clinical presentations, pathogenic mechanisms and options for management of MELAS syndrome.

Patients with MELAS with negative myopathology for characteristic ragged-red fibers

BACKGROUND

Muscle pathology usually contributes to mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episode (MELAS), even in patients without prominent muscle symptoms. We report a series of patients with MELAS without significant myopathic changes.

METHODS

Twelve patients without ragged-red fibers (RRFs) on muscle pathology (RRF-negative group) and 99 patients with MELAS and RRFs and/or cytochrome c oxidase (COX)-deficient fibers (control RRF-positive group) were recruited. We analyzed clinical features, neuroimaging and pathological findings, gene mutation data, immunofluorescence assay of key respiratory chain subunits of complexes I and IV and mitochondrial DNA (mtDNA) mutation load in biopsied muscle samples.

RESULTS

None of the RRF-negative patients had RRF or COX-negative fibers, but four patients had strongly succinate dehydrogenase-stained vessels (SSVs). There was a lower proportion of m.3243A>G and higher proportion of mitochondria-encoded ND gene mutations in RRF-negative than RRF-positive patients. The proportion of aphasia was relatively higher, while complex I and IV subunit abundance in muscle and mutation load were lower in RRF-negative than in RRF-positive patients.

CONCLUSION

RRF-negative patients had a similar disease course, clinical symptoms, and neuroimaging results to RRF-positive patients with MELAS. SSV is a valuable diagnostic indicator for MELAS. For highly suspected MELAS yet without positive myopathological findings, combined immunofluorescence and genetic studies should be used to achieve final diagnosis.