OBJECTIVES: Primary mitochondrial disease (PMD) is characterized by a variety of signs/symptoms that can negatively impact patients’ daily lives. This research aimed to describe the key PMD signs/symptoms and disease impacts from the perspective of PMD patients. METHODS: Concept elicitation interviews were conducted with PMD patients (N=20) to identify and better understand the signs/symptoms and impacts that characterize the disease experience. In open-ended, one-on-one interviews with trained researchers, subjects discussed their PMD experiences and rated the bother of their signs/symptoms. Transcribed interviews were coded and analyzed and results were summarized in a PMD conceptual model. RESULTS: Saturation analysis of the 47 PMD sign/symptom concepts elicited from patients confirmed the adequacy of the sample size. Mean age of participants was 42.7 years (SD=13.5), 11 were male (55.0%), and a range of PMD phenotypes were represented. The most frequently reported signs/symptoms were fatigue/tiredness (n=15, 75.0%), impaired vision (n=12, 60.0%), memory problems (n=7, 35.0%), balance problems (n=7, 35.0%), numbness (n=6, 30.0%), headache (n=6, 30.0%), muscle pain (n=6, 30.0%), and muscle weakness (n=6, 30%). Of concepts rated by at least two participants, balance problems and fatigue/tiredness had the highest mean bother ratings (8.5 and 8.09, respectively, on a 0-10 numeric rating scale). All 15 participants who reported fatigue deemed it an important symptom to improve with effective treatment. Though participants reported a variety of ways that PMD impacts their daily life (n=59), the most frequently reported were on ability to work/attend school (n=16), interact socially (n=15), exert oneself physically (n=15), and perform at work/school (n=14). CONCLUSIONS: Results confirmed PMD to be a symptomatically bothersome and impactful condition from the perspective of patients with the disease and, moreover, will be of immediate use to researchers and healthcare providers wishing to identify meaningful outcomes for their PMD patients.