Perceived fatigue is highly prevalent and debilitating in patients with mitochondrial disease

Highlights • Perceived fatigue is a prominent and often debilitating symptom in patients with mitochondrial disease. • Perceived fatigue correlates with disease severity but not genotype. • Excessive sleepiness is prevalent but dissociated with perceived fatigue in patients with mitochondrial disease. • Perceived fatigue does not correlate with NMDAS muscle weakness scores. • Our findings have important implications for targeting of pharmacological therapies.