]> 2026-07-31T07:52:14+00:00 WBR0245 0 en Brain MRI A patient with stroke-like symptoms and lactic acidosis suggests MELAS syndrome. An MRI might show increased signals in the posterior cerebrum during an episode, but these findings are not usually diagnostic of MELAS. Blood smear Hematologic diseases, such as G6PD deficiency, can cause lactic acidosis due to hemolysis. However, lactic acidosis of G6PD is not typically as severe as the acidosis in this patient. Furthermore, G6PD is an X-linked condition and is therefore highly unlikely to occur in a woman. Muscle biopsy Ragged red fibers on muscle biopsy are characteristic of mitochondrial diseases, including MELAS. Glucose tolerance test A glucose tolerance test is helpful to diagnose diabetes mellitus. Liver enzymes Liver enzymes are not classically elevated in MELAS. Genetics A 19-year-old woman is brought to the emergency department (ED) by EMS for transient loss of consciousness. Her roommate reports that she was watching television when she began to see the colors on the screen blend, and the room began to “wave”. As her vision normalized, she experienced a sharp migraine-like headache and vomited twice. She lost consciousness for 10 minutes but regained consciousness by the time EMS arrived. The patient explains that this is not the first time she experiences stroke-like symptoms, and she had multiple similar episodes in the past. Her past medical history is also significant for multiple hospitalizations for tonic-clonic seizures. Upon further investigation, the woman states that she has been intolerant to exercise ever since she was a child. Physical examination in the ED is remarkable for transient weakness in the right upper and lower limbs and a wide-based, ataxic gait. Laboratory studies demonstrate elevated serum lactate concentration. What is the most appropriate diagnostic modality for this patient's condition? C General Principles 2020-10-27T23:53:54Z 2459150.4957639 WBR0245