Papers of the Week

Fatigue and exercise intolerance have been only rarely reported as initial- and sole-onset manifestations of a mitochondrial disorder (MID). We present a patient with nonsyndromic MID with fatigue and exercise intolerance as its initial manifestations of the disease. . A 39 yo female experienced fatigue since age 18 and exercise intolerance since age 21. Later on, she developed Hashimoto thyroiditis, recurrent diffuse headache, and double vision upon exercise. Clinical exam revealed short stature, bilateral ptosis, partially reduced tendon reflexes, and hypertrophic calves. Serum lactate was elevated, and the lactate stress test was abnormal. Workup for suspected MID revealed ragged-red fibers and NADH-deficient muscle fibers, and biochemical investigations revealed a mild complex-I defect. mtDNA sequencing revealed the variant m.3243A>G with a heteroplasmy rate of 70% in the muscle.