The profound implications of mitochondrial myopathy on activities of daily living: an observational qualitative study of standardized structured and semi-structured patient interviews.

Background: The impact of Mitochondrial Myopathy (MM) symptoms on functional ability across activities of daily living (ADLs) has not been fully characterized, nor is it understood how MM patients define their key symptoms. Furthermore, it is unclear what MM individuals perceive as a clinically meaningful improvement. Objective: We sought to characterize how MM patients feel about their symptoms in the key MM domains of muscle weakness, muscle fatigue, exercise intolerance, imbalance, and peripheral neuropathy; as well as their functional ability. Design: We conducted a single-center, observational, qualitative study that involved standardized structured and semi-structured patient interviews. Methods: Most interview questions were open-ended, allowing individuals to provide personalized narratives that were transcribed in real time. A total of 33 individuals with MM were interviewed either in-person or remotely. Interview transcripts underwent thematic analysis in accordance with grounded theory. Data was presented using a mixed-methods approach. Results: Subjects provided extensive narratives that demonstrated the substantial and widespread impact of MM across many aspects of MM patient lives, including the impact of each MM domain of muscle weakness, muscle fatigue, exercise intolerance, imbalance, and peripheral neuropathy on ADLs; the need to adapt to preserve independence and quality of life (QOL); impaired self-perception, participation in social activities, hobbies, and relationships; and change in circumstances over time. Conclusion: These meaningful insights highlight the critical and emergent need for approved drug treatment(s) in this profoundly burdened patient population. Our results will serve as a comprehensive resource to inform the physician, patient, industry and advocacy communities on outcome measure selection and clinical trial design; and to help inform regulatory agencies in the United States Food and Drug Administration (FDA) drug approval process for MM.