Mitochondrial disorders: a descriptive study of a Tunisian pediatric series

Introduction: Mitochondrial disorders (MD) represent a heterogeneous group of rare and often misdiagnosed metabolic disorders. There are few descriptive studies of large pediatric series both at the national and international level. Our objective was to describe the demographic, clinical, paraclinical and evolutionary characteristics of a Tunisian cohort followed for MD. Methods: A longitudinal retrospective study of patients followed in the pediatric neurology department at the National Institute Mongi Ben Hmida of Neurology in Tunis between 2004 and 2021 for MD. Demographic, clinical, paraclinical and evolutionary data were collected and analyzed. The different clinical phenotypes have been identified. Results: One hundred and one patients were included. The sex-ratio was 1.1. About 75% of the patients had an onset before the age of two years. Neurological manifestations were dominated by abnormalities of psychomotor development, movement disorders, seizures, and pseudoencephalitic episodes. Brain magnetic resonance imaging showed signal abnormalities in the basal ganglia, supra tentorial white matter and brainstem in 46,5%, 35,6% and 30,7% of cases, respectively. The predominant mitochondrial phenotype was Leigh syndrome (LS) (51.4%). The genetic study of LS revealed a prevalence of mutations in the genes encoding thiamine transporters, found in eight patients. Conclusion: Our study highlights the clinical and radiological heterogeneity of MD. LS remains the most frequent MD. Genetic confirmation should not delay initiation of therapy with Thiamine and Biotin in case of any LS, which may improve the prognosis in case of thiamine metabolism dysfunction syndrome.
Keywords: Mitochondrial disorders, Leigh syndrome, Thiamine metabolism dysfunction syndrome