Am J Case Rep. 2021 Apr 19. 22
e930175
BACKGROUND The normalization of serum lactate levels in a patient with non-syndromic mitochondrial disorder due to the m.3243A>G mitochondrial DNA (mtDNA) variant has not been previously reported. CASE REPORT A 57-year-old woman was diagnosed with mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) due to the m.3243A>G variant, with low heteroplasmy rates (31%), at age 50. The initial manifestations were short stature, migraine, and diabetes. With progression of the disease, multisystem involvement developed, affecting the brain (stroke-like episode, mild cognitive impairment), eyes (pigmentary retinopathy), ears and the vestibular system (impaired hearing, tinnitus, imbalance, drop attacks, vertigo), intestines (constipation, distended abdomen, gastro-esophageal reflux, gastroparesis), and the muscles (muscle weakness). The gastrointestinal involvement was most prominent and most significantly lowered the patient's quality of life. The diabetes was well controlled with an insulin pump. Recurrent, acute deteriorations responded favorably to L-arginine. Owing to lifestyle and diet changes 2 years after diagnosis (start of art classes, increase in spin biking to 22.5 km 3 times per week, travel to Hawaii, adherence to low-carbohydrate high-protein diet), the patient managed to lower elevated serum lactate levels to largely normal values. CONCLUSIONS Gastrointestinal compromise may be the prominent manifestation of the m.3243A>G variant, lifestyle and diet changes may lower serum lactate in m.3243A>G carriers, and low heteroplasmy rates of the m.3243A>G variant in scarcely affected tissues do not exclude pathogenicity.