Patient and healthy control recruitment criteria
Nine adult patients referred to the NHS Specialised Services-funded Mitochondrial Diagnostic Centre in London for investigation of CPEO and found to harbour a single, sporadically occurring, mtDNA deletion in skeletal muscle, and nine age- and gender-matched healthy controls were recruited. The mean age of the patients was 33 years (range: 19–52 years) with a mean age at symptom onset of 16 years (range: 12–32 years). Four patients with a clinical diagnosis of Kearns-Sayre syndrome (KSS) had a mean age at onset of 12 years (range: 6–17 years). The remaining patients with CPEO had a mean age of onset of 20 years (range: 14–32 years). The mean age of the controls was 33 years (range: 26–43 years).
Institutional Research Ethics Committee approval for the study, and accordingly individual subjects’ consent, was obtained.