Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome mimicking herpes simplex encephalitis: A case report.

Mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome presents with the features of herpes simplex encephalitis (HSE), which is rare and has been described in only a few case reports. Our case describes a 17-year-old female with no significant previous medical history presenting with an acute onset of fever, headache, and epilepsy, similar to HSE. Computed tomography of the brain showed bilateral basal ganglia calcification. Magnetic resonance imaging demonstrated gyriform restricted diffusion with T2-weighted images prolongation. Further investigation showed elevated blood lactate concentration at rest. Hence, MELAS was suspected and the diagnosis was confirmed by the presence of a nucleotide 3243 A→G mutation in the mitochondrial DNA. The clinical presentation and imaging studies of MELAS are variable and may mimic those of HSE. Infection may have also precipitated MELAS manifestation in this patient. Laboratory features, such as elevated lactate, basal ganglia calcification, and gyriform restricted diffusion may be helpful in identifying patients with MELAS.