Table 2.
Classification of the more common forms of mitochondrial diseases on the basis of genetics
| Genome | Gene | mtDNA | Clinical phenotype |
|---|---|---|---|
| mtDNA | Single deletion | KSS, ocular myopathy, PS | |
| mtDNA | tRNALeu(UUR) | Single deletion | MELAS |
| tRNALys | Single deletion | MERRF | |
| Other tRNAs | Single deletion | Multiple phenotypes | |
| ATPase6 | Single deletion | NARP/MILS | |
| ND1, ND4, ND6 | Single deletion | LHON | |
| ND1, ND4 | Single deletion | Myopathy, multisystemic diseases | |
| Cyt b | Single deletion | Myopathy, multisystemic diseases | |
| COX III | Single deletion | Myopathy, multisystemic diseases | |
| nDNA | SCO1 | Single deletion | Hepatoencephalomyopathy |
| SCO2 | Single deletion | Cardioencephalomyopathy | |
| COX10 | Single deletion | Nephroencephalomyopathy | |
| COX 15 | Single deletion | Cardioencephalomyopathy | |
| ATP 12 | Single deletion | Fatal infantile | |
| TP | Multiple deletions | MNGIE | |
| ANT1 | Multiple deletions | adPEO* | |
| Twinkle | Multiple deletions | adPEO* | |
| POLG | Multiple deletions | ad/arPEO* | |
| dGK | Depletion | Hepatocerebral syndrome | |
| TK2 SMA | Depletion | Myopathy, SMA | |
| TAZ | Depletion | Barth syndrome | |
| OPA1 | Depletion | Optic atrophy |
ad/arPEO: Autosomal recessive progressive external ophthalmoplegia; adPEO: autosomal dominant progressive external ophthalmoplegia; ANT1: adenine nucleotide translocator-1; ATP: adenosine triphosphate; ATPase6: adenosine triphosphate synthase 6; COX: cyclooxygenase; Cyt b: cytochrome B; DGK: diacylglycerol kinase; KSS: Kearns- Sayre syndrome; LHON: leber hereditary optic neuropathy; MELAS: mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes; MERRF: myoclonic epilepsy with ragged-red fibers; MILS: maternally inherited leigh syndrome; MNGIE: mitochondrial neurogastrointestinal encephalomyopathy; NARP: neuropathy, ataxia and retinitis pigmentosa; ND1,4 and 6: NADH dehydrogenase subunit 6; OPA1: mitochondrial dynamin like GTPase; POLG: DNA polymerase subunit gamma; PS: Pearson’s syndrome; SCO1: synthesis of cytochrome c oxidase 1; SMA: spinal muscular atrophy; TAZ: tafazzin; TK2: thymidine kinase 2. mtDNA indicates alteration in mtDNA secondary to nDNA mutations. *Indicates proximal weakness, neuropathy, psychiatric disorders, parkinsonism. Information in Table 2 is modified from the studies of DiMauro (2004) and Muravchick (2008).