Delayed Diagnosis of Adult-Onset Melas Syndrome: A Case Report And Literature Review

Background: Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke-like Episodes (MELAS) syndrome is a rare inherited mitochondrial disorder that can present in adulthood with a wide range of clinical manifestations, often mimicking other neurological conditions. We report a case of adult-onset MELAS that was initially misdiagnosed to highlight the diagnostic challenges and underscore the importance of appropriate management of this condition. Case presentation: A 37-year-old Vietnamese male with no previous medical history was admitted with bilateral sensorineural hearing loss and mild dysarthria. Initial brain magnetic resonance imaging (MRI) revealed diffusion restriction in the left temporoparietal region without evidence of vascular occlusion or stenosis, and the patient was initially diagnosed with ischemic stroke. Over the following four months, the patient developed progressive right-sided hemiparesis, generalized seizures, and altered consciousness. Follow-up MRI revealed cerebral atrophy, along with diffuse, migratory lesions not conforming to vascular distributions and without diffusion restriction. Magnetic resonance spectroscopy (MRS) revealed an inverted doublet lactate peak and reduced N-acetyl aspartate (NAA) levels. Serum lactate was mildly elevated at 2.61 mmol/L. Genetic testing identified an m.3243A>G mutation with a heteroplasmy level of 9%, confirming the diagnosis of MELAS syndrome. Supportive treatment with L-arginine, coenzyme Q10 (CoQ10), riboflavin, appropriate antiepileptic drugs, and a ketogenic diet (KD) resulted in good seizure control and improvement in neurological function. Conclusion: Adult-onset MELAS syndrome is a rare mitochondrial disorder that can mimic other neurological diseases. Early recognition enables appropriate management and helps avoid potentially harmful treatments.