Our aim was to evaluate the impact of Paramyotonia Congenita on quality of life (QoL), in a cohort of Tunisian patients and assess its correlation to clinical symptoms.

Paramyotonia congenita (PMC) is a rare autosomal dominant muscular channelopathy, its impact on QoL remain poorly characterized.

We conducted a descriptive cross-sectional study that included patients from the same family followed for PMC at the Neurology Department of Razi Hospital, Tunis, Tunisia, from January 2022 to December 2022. We collected their clinical data. We performed exons-sequencing of the SCN4A gene. The impact on patients' QoL was assessed by the Individualized Neuromuscular Quality of Life Questionnaire (INQoL).

We included 30 patients. The median age was 36.5 years. Clinical assessment identified paradoxical myotonia exacerbated by cold (100%), transient paralysis (77%), muscle hypertrophy (67%), myalgias (43%), and permanent motor deficits (20%). Genetic analysis revealed the presence of the p.Thr1313Met mutation in the SCN4A gene. Total INQoL score was at 43.3 (33.3-53.9). Most impactful symptom on the QoL was myotonia 84.21 (57.89-94.73), followed by weakness at 63.15 (23.68-78.94), pain 31.57 (0-85.5), and fatigue 0 (0-78.94). Among the affected domains, activities were the most affected at 65 (36-80), followed by impaired autonomy at 58.3 (30.55-72.22), impact on physical appearance at 50 (16.66-66.66), relationships with others at 49.16 (29.58-69.5) and emotional well-being at 34.72 (19.44-59.72). Duration of grip myotonia was correlated with the severity of myotonia as assessed by the INQoL (p=0.039, Rho=0.5). Duration of paralysis was significantly correlated with scores weakness score (p=0.015, Rho=0.55) and the overall INQoL score (p=0.019, Rho=0.45).

Our study has demonstrated that QoL was substantially impaired in our patients with PMC. Further, Myotonia was the most impactful symptoms. There was a positive correlation between the objective clinical signs and their perceived impact, as assessed by the INQoL.