MELAS (Mitochondrial Myopathy and Encephalopathy, Lactic Acidosis, and Stroke Episodes)

A 43-year-old female presented with complaints of sudden-onset blurred vision in both eyes this afternoon. She reported a past medical history of bilateral hearing impairment, type 1 diabetes mellitus, and hypertension. Her family history was positive for type 1 diabetes mellitus. Since yesterday, the patient had been experiencing nausea and diarrhea. Her headaches began in the morning, and by the afternoon, she reported blurred vision. At the emergency room, her vision was finger counting at 20 cm in the right eye and hand motion at 50 cm in the left eye. Intraocular pressures were normal. Her eyeballs showed nystagmoid movement with a fast phase to the left. There was full range of eye motion. Slit lamp examination showed normal anterior segments. Pupil response was also normal. Ophthalmoscopic examination revealed bilateral temporal optic disc pallor (Fig. 21.1). A confrontation test showed homonymous left field defects in both eyes. A CT scan of the brain showed symmetric calcification over the bilateral caudate, putamen, and pallidum (Fig. 21.2). Elevated blood lactate (22.2 mg/dL) was noted, and supportive treatment was given during the acute period. A brain MRI also revealed similar lesions in the basal ganglion which were hyperintense on a T1-weighted image and hypointense on FLAIR and T2-weighted images (Fig. 21.3). In addition, there was a diffuse, hyperintense lesion over the right temporo-occipital area on T2-weighted, FLAIR, and diffusion scans. However, the lesion did not show low values on ADC on the second day after onset (Fig. 21.4) and became depressed on the fourth day (Fig. 21.5). A visual field examination on the fourth day showed near total obscuration in both eyes (Fig. 21.6). Muscle biopsy showed nonspecific type 2 muscle atrophy. Peripheral blood DNA analysis revealed a mtDNA 3243 A>G mutation. The patient was diagnosed with mitochondrial myopathy and encephalopathy, lactic acidosis, and stroke episodes (MELAS). On the eighth day, her vision recovered to 6/8.6 in the right eye and 6/10 in the left eye. Four months later, her visual field recovered almost completely (Fig. 21.7).