Clinical and Molecular Characterizations of Mitochondrial Disorders: A Tertiary-Care Center Experience

Background: Given the limited research on mitochondrial diseases in our area, specifically regarding their genetic variability and diverse clinical manifestations, and considering the significant number of consanguineous marriages in our region, we aimed to investigate the clinical and molecular characteristics of patients with mitochondrial disorders in Saudi Arabia. Methods: This retrospective cross-sectional cohort study involved a chart review of patients diagnosed with mitochondrial disorders at the Ministry of National Guard Health Affairs tertiary health care centers in Saudi Arabia between 2013 and 2022. Results: The study population comprised 116 patients with a mean age of 10 years (±7 SD). Among the study cohort, 34.5% (n = 40) had died. The primary cause of death was cardiopulmonary arrest (55.0%, n = 22). The most prevalent condition was developmental delay (67.9%. Around 56.9% were diagnosed using Whole Exome Sequencing (WES), 10.3% by Whole Genome Sequencing due to negative WES, 23.3% through a single-gene approach, 7.8% were analyzed through a mitochondrial panel, and 1.7% via a gene panel. The distributions of current age and age at diagnosis were significantly different between the nuclear and mitochondrial gene types. Notably, the diagnostic delay time (time taken from symptom onset to genetic diagnosis) averaged 1.5 years for nDNA variants compared to an average of 10 years for mDNA variants. Conclusions: This study shows that gene type affects clinical characteristics, highlighting the importance of genetic studies in disease manifestation.