| Cardiac involvement | Cardiomyopathy, cardiac conduction defects, complete heart block<sup>[1]</sup> |
| Muscle biopsy | Ragged-red fibers on modified Gomori trichrome staining |
| Serum and CSF lactate | Typically elevated |
| Mitochondrial DNA analysis | Detection of large-scale deletions |
| CSF protein | Usually >100 mg/dl |
| ECG/EKG | May show conduction abnormalities |
| Databases | OMIMOrphanetClinicalTrialsPubMed |