[Mitochondrial encephalopathy, lactic acidosis and stroke-like episodes / myoclonus epilepsy with ragged-red fibers /Leigh overlap syndrome caused by mitochondrial DNA 8344A>G mutation]

Phenotypic heterogeneity of the mitochondrial DNA A8344G variant presenting with dorsal midbrain syndrome

Purpose

To describe a neuro-ophthalmic presentation of a phenotypically heterogeneous mitochondrial DNA variant.

Observations

A 10-year-old female with gross motor developmental delay, absence seizures and ataxia subacutely developed poor near acuity and asthenopia. She was found to have accommodative insufficiency, impaired supraduction and convergence retraction nystagmus leading to a diagnosis of dorsal midbrain syndrome. Brain MRI showed highly symmetrical lesions involving the dorsal pons. Genetic testing revealed a previously undiagnosed mitochondrial DNA (mtDNA) pathogenic variant, adenine to guanine at nucleopeptide pair 8344 (A8344G).

Conclusion and importance

The authors describe a unique, neuro-ophthalmic manifestation of mitochondrial disease in a pediatric patient. This report discusses the phenotypic heterogeneity of the mtDNA A8344G variant, which may include 'stroke-like episodes' involving the brainstem, thus presenting with ophthalmic manifestations.

Familial mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episode syndrome: Three case reports

BACKGROUND

Mitochondrial encephalomyopathy (ME) is a multisystem metabolic disease that primarily affects the central nervous system and skeletal muscle. It is caused by mutations in mitochondrial or nuclear DNA, resulting in abnormal mitochondrial structure and function and insufficient ATP synthesis. The most common subtype is mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episode (MELAS) syndrome. In recent years, reports of MELAS syndrome have increased but familial cases are rare.

CASE SUMMARY

We report a case of familial MELAS syndrome. Cases 2 and 3 are sisters and case 1 is their nephew. All are short in stature and showed stroke-like episodes with rapid onset and no obvious symptoms such as paroxysmal headache, aphasia, or blurred vision. After admission, blood lactate levels were significantly higher than normal. The patients underwent magnetic resonance imaging of the head. Cases 1 and 2 were considered to have ME, whereas case 3 was considered to have a space-occupying lesion in the left temporal lobe. Pathological evaluation showed no obvious tumor cells in the brain lesions of case 3. Muscle biopsy or genetic test results were consistent with ME. The patients were diagnosed with MELAS syndrome and their symptoms improved with intravenous infusions of coenzyme Q10, coenzyme A, vitamin B, and vitamin C. At the 6 mo follow-up, there was no recurrence or progression.

CONCLUSION

When a patient has MELAS syndrome, familial MELAS syndrome should be considered if related family members have similar symptoms.