Adult onset MELAS Syndrome Presenting as A Mimic of Herpes Simplex Encephalitis.

Purpose: Mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS) syndrome primarily affects the young and may not be considered first in an older adult with infection-like encephalopathy. Here, we present the case of a patient who suffered from the acute onset of fever, delirium, and epilepsy, mimicking herpes simplex encephalitis (HSE).

Case report: A 52-year-old woman with diabetes and end stage renal disease (ESRD) regularly took oral anti-diabetic drugs (OADs) and received hemodialysis. She presented with an acute onset of fever, delirium, and epilepsy, mimicking HSE. Further investigation showed a persistent elevated lactate level in the cerebrospinal fluid (CSF). A mitochondrial DNA analysis revealed a point mutation at nucleotide 3243.

Conclusion: The clinical presentation and imaging studies of MELAS in adults are variable and may mimic those of HSE. Antiviral therapy should be administered until the diagnosis of MELAS is definitive. Infection and metformin may have also precipitated MELAS manifestation in this patient. Clinicians should avoid potential mitochondrial-toxic drugs in these patients.