ESPE Abstracts

Introduction: Monocarboxylate transporter 8 (MCT8) deficiency is an ultra-rare genetic disease, associated with severe cognitive and motor disability and symptoms of chronic peripheral thyrotoxicosis. The aimof this analysis is to describe the HRQoL impact experienced by patients with MCT8 deficiency as described by their caregivers.

Methods: Informal caregivers of patients with MCT8 deficiency completed an online cross-sectional survey, including questions about their care recipient such as age and functioning. As assessing HRQoL directly from patients with MCT8 deficiency can be challenging, caregivers completed the EQ-5D-5L proxy version 1 to rate their care recipient’s HRQoL. The EQ-5D-5L assesses current health and includes a descriptive system with five dimensions (i.e., mobility, self-care, usual activities, pain/discomfort, and anxiety/depression), each with five levels.

Results: Twenty-two caregivers residing in the United Kingdom, United States, Canada, France, Netherlands, Italy, and Germany participated in the study. The mean age of the patients with MCT8 deficiency was 8.8 years, ranging from 0.8 to 30.4 years. Over half (54.5%) had no head control and none could sit or walk without support. Approximately one-fifth (18.2%) were able to express themselves to their caregivers (e.g., through gestures, facial expression or voice), 72.7% could respond when their caregiver spoke to them and 9.1% could not respond. The majority of patients with MCT8 deficiency were unable to walk (72.7%), wash or dress themselves (77.3%) or carry out their usual activities (68.2%). Over half (54.5%) had slight pain or discomfort and over one-third felt slightly anxious or depressed (36.4%).

Conclusion: In the majority of cases, caregivers of patients with MCT8 deficiency identified their care recipients to have impaired physical functioning (head control, sitting and walking). In terms of communication, most patients with MCT8 deficiency were able to express themselves and respond when spoken to. As caregivers were not asked to specify the means of expression used by their care recipient, future research could explore this aspect further. Scores for mobility, self-care and usual activities met expectations; most caregivers reported that the patient with MCT8 deficiency had no head control, and that those with head control were unable to sit or walk without support. The impacts on the pain/discomfort and anxiety/depression domains were variable. No disease-specific instrument exists for MCT8 deficiency and the EQ-5D-5L has limitations as a generic instrument. Future research could contextualize these findings using EQ-5D-5L scores from other ultra-rare diseases with similar symptom profiles.