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Late-onset Mitochondrial Encephalopathy, Lactic Acidosis, and Stroke-like Episodes Presenting With Auditory Agnosia

Smith, Kelsey, MD*; Chiu, Shannon, MD; Hunt, Christopher, MD; Chandregowda, Adithya, PhD*; Babovic-Vuksanovic, Dusica, MD§; Keegan, B. Mark, MD*

doi: 10.1097/NRL.0000000000000229
Case Report/Case Series
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Introduction: Mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) is a multisystemic mitochondrial disorder that usually presents in childhood. Patients can have a wide array of neurological symptoms when presenting with stroke-like episodes, and imaging characteristics during the episodes can overlap with different neurological disorders.

Case Report: A 61-year-old woman presented with communication difficulties consistent with auditory agnosia and was found to have bitemporal abnormalities on imaging that first raised the concern for herpes simplex virus encephalitis. Further work-up, in conjunction with the patient’s past medical and family history, suggested a mitochondrial disorder. Mitochondrial full genome analysis revealed m.3243A>G variant in the MT-TL1 gene, with 6% heteroplasmy in blood leading to a diagnosis of MELAS.

Conclusions: MELAS is a disorder with clinical variability. Neuroimaging studies during stroke-like episodes in MELAS can provide significant clues to the underlying disorder. Although patients typically present in childhood, the first stroke-like episode can occur later in life in some patients, potentially related to a lower heteroplasmy level.

Departments of *Neurology

Radiology

§Clinical Genomics, Mayo Clinic, Rochester, MN

Department of Neurology, University of Florida, Gainesville, FL

B.M.K. has research funded by Biogen, and receives publishing royalties for Common Pitfalls in Multiple Sclerosis and CNS Demyelinating Disease. The remaining authors declare no conflict of interest.

Correspondence to: B. Mark Keegan, MD, Mayo Clinic, 201 First St. SW, Rochester, MN 55905. E-mail: keegan.bmark@mayo.edu.

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