ObjectiveTo describe the prevalence and characteristics of sleep-disordered breathing (SDB) in a large cohort of patients with genetically confirmed mitochondrial diseases.MethodsThis is a prospective observational study performed at the Neurophysiopatology Unit of Fondazione Policlinico Universitario A. Gemelli IRCCS. All participants had a defined mitochondrial disease and were investigated by full-night polysomnography.ResultsOne hundred three consecutive patients were enrolled. SDB was demonstrated in 49 patients (47.6%). Regarding phenotypes, we found differences in distribution between the groups: patients affected by progressive external ophthalmoplegia with single or multiple mtDNA deletions frequently had obstructive apneas (50% and 43.8%) or REM-related hypoventilation when associated with m.3243A>G mutations (75%). Furthermore, a high percentage of participants with maternally inherited diabetes and deafness and myoclonic epilepsy with ragged-red fibers syndromes were characterized by obstructive sleep apnea and REM-related hypoventilation, respectively. In contrast to what has been described in previous studies, central sleep apnea was rarely reported in our cohort.ConclusionsSDB has a higher prevalence in mitochondrial diseases compared to general population–based data. Overall, these results suggest that patients characterized by a specific phenotype-genotype combination are most at risk of developing a specific subgroup of SDB. The early identification of this disorder is crucial in the management of these fragile patients.