Patients’ lived experience of thymidine kinase 2 deficiency: the online survey-based assessment of TK2d patient perspectives study

Abstract

Background: Thymidine kinase 2 deficiency (TK2d) is an ultra-rare autosomal recessive mitochondrial disease characterized by progressive myopathy. Objectives: To understand patient experiences and the impact of TK2d on patient quality of life (QoL), and to explore support needs. Design: A cross-sectional international online survey. Methods: The survey for the Assessment of TK2d Patient Perspectives (ATP) study, co-created with patient advocates, included multiple-choice questions, verbal rating scales, and open free-text questions. Patients of all ages with a self-reported genetic diagnosis of TK2d were eligible to participate, either directly or through a caregiver proxy. The patient, caregiver proxy, or bereaved caregiver proxy answered questions on demographics, signs/symptoms, impacts on health-related QoL (HRQoL), support needs, healthcare resource use, and overall experience of living with TK2d. Quantitative data were summarized with descriptive statistics. Qualitative data were analyzed using inductive thematic analysis. Results: Responses for 32 patients (24 patient and 8 caregiver proxy responses) were collected between September 2023 and February 2024. All patients experienced myopathic symptoms. The most frequently reported impact of TK2d was on patients’ ability to perform basic activities of daily living (26/32), including difficulties in walking (22/32), eating/swallowing (19/32), and breathing (25/32). The proportions of patients reporting a moderate or severe impact of breathing and walking difficulties on HRQoL, and the proportions requiring medical devices, were higher for those with an earlier age of TK2d symptom onset (⩽2, vs >2 to ⩽12, or >12 years). For most patients, TK2d also had a negative impact on mood, social and leisure activities, and employment/education. Progressive loss of abilities, increasing dependency on others, and medical equipment use contributed to mental and emotional burdens. Conclusion: These quantitative and qualitative analyses of patients’ lived experiences highlight the substantial, progressive, and wide-ranging burden of TK2d.