Patients’ lived experience of thymidine kinase 2 deficiency (TK2d): results from the Assessment of TK2d Patient Perspectives (ATP) study

Topic:

Other

Poster Number: P252

Author(s):

Philip Yeske, PhD, United Mitochondrial Disease Foundation, Pittsburgh, PA, USA, Cristy Balcells, UCB, Smyrna, GA, USA, Asha Hareendran, MA, PhD, UCB, Slough, UK, Alexandra Morrison, Rare Disease Research Partners, Amersham, UK, Marnie Ross, Rare Disease Research Partners, Amersham, UK, Katie Waller, The Lily Foundation, Warlingham, UK, Amel Karaa, MD, Massachusetts General Hospital, Genetics Division, Harvard Medical School, Boston, MA, USA

Introduction:
Thymidine kinase 2 deficiency (TK2d) is an ultra-rare, genetic, mitochondrial disease, associated with progressive, life-threatening myopathy that affects motor function, breathing and feeding. The aim of this study was to capture patients’ and caregivers’ experiences of TK2d and its impact on patients’ health-related quality of life (HRQoL). Patient findings are presented here.

Methods:
Individuals with genetically confirmed TK2d (or proxy caregivers) were invited to complete an online mixed-methods survey co-created by a patient steering committee. The survey was shared via mitochondrial disease patient organizations from September 2023 to February 2024.

Results:
Thirty patients/proxy caregivers (median patient age [range]: 31 [2–54] years) and two bereaved caregivers from 12 countries participated. Most responses were about patients aged ≥16 years (n=26). Three ‘age of TK2d symptom onset’ phenotypes from literature were equally represented (≤2 [n=12], >2 to ≤12 [n=10] and >12 [n=10] years). Eight patients were receiving/had previously received pyrimidine nucleoside therapy via compassionate use.
The most frequent TK2d signs/symptoms were categorized as muscular/myopathy (n/N=32/32), neurological (n/N=29/32) and psychological (n/N=25/32). The impacts of TK2d most frequently reported were walking/eating/toileting (n/N=26/32), breathing (n/N=25/32), development (delayed/loss of ability, n/N=20/32) and feelings of isolation (n/N=17/32). Difficulties with lower body muscle weakness/walking, breathing and fatigue most negatively affected patients’ HRQoL. Of those who rated impact levels, 12/22, 7/25 and 5/19 reported an ‘extreme’ impact on their HRQoL due to walking, breathing and eating/swallowing difficulties, respectively.
Most patients (78.1%, n/N=25/32) needed home modifications and support to help with daily activities; 12.5% (n/N=4/32) required full-time medical support.

Conclusions:
The clinical manifestations experienced by patients with TK2d are associated with debilitating physical impacts and severe psychological strain. This reflects the high burden of TK2d and its impact on patients’ HRQoL. Walking, breathing and eating/swallowing difficulties were reported as having ‘extreme’ impact on HRQoL by some patients.

Study funded by UCB.