Table 1.
Clinical, biochemical, and histopathological data in the whole cohort of patients classified as having nuclear DNA (nDNA) or mitochondrial DNA (mtDNA) mutations. Results are expressed as the percentage of cases with impaired biomarkers (elevated concentration above normal cut-off value), percentage of patients presenting with myopathic features, and percentage of muscle biopsies with positive features. Chi-square was calculated to look for associations between the different variables listed in the left column (categorized as presence or absence) and whether the mutation was in the nDNA or mtDNA. nDNA patients showed a higher frequency of succinate dehydrogenase (SDH) reduction and SDH-positive vessels, while mtDNA patients showed a higher frequency of ragged red (RRF) and blue fibers.
| Percentage (%) | Total Group (n = 103) | nDNA Patients (n = 59) | mtDNA Patients (n = 44) | Chi-Square |
|---|---|---|---|---|
| Sex (M/F) | 58.3/41.7 | 57.6/42.4 | 59.1/40.9 | n.s. |
| Exitus | 41.7 | 40.6 | 44.4 | n.s. |
| Survival (years) | 6.7 | 11.9 | n.s. | |
| Biomarkers | ||||
| Lactate | 79.8 | 81.5 | 77.5 | n.s |
| Pyruvate | 69.1 | 76.1 | 60.0 | n.s. |
| Alanine | 64.9 | 61.1 | 70.0 | n.s |
| Organic acids | 35.3 | 34.0 | 37.5 | n.s |
| GDF-15/FGF-21 | 51.4 | 48.0 | 60.0 | n.s |
| Myopathy | ||||
| CPK | 28.3 | 37.1 | 16.0 | n.s. |
| Ophthalmoplegia | 23.4 | 15.9 | 33.3 | n.s. |
| Myopathic facies | 20.8 | 16.3 | 26.5 | n.s. |
| Exercise intolerance | 25.3 | 16.7 | 36.4 | n.s. |
| Weakness | 26.0 | 22.7 | 30.3 | n.s. |
| Rhabdomyolysis | 3.9 | 4.7 | 2.9 | n.s. |
| EMG (myopathic) | 19.9 | 18.5 | 23.5 | n.s. * |
| Histopathology | ||||
| RRF | 32.8 | 18.2 | 50.0 | 6.959 (p = 0.008) |
| Blue fibers | 36.0 | 20.0 | 60.0 | 8.333 (p = 0.004) |
| COX negative | 39.6 | 41.4 | 36.8 | n.s. |
| COX reduction | 50.0 | 51.7 | 47.4 | n.s. |
| SDH reduction | 22.4 | 34.5 | 5.0 | 5.910 (p = 0.015) |
| Positive SDH (Vessels) | 65.8 | 85.7 | 41.2 | 8.828 (p = 0.004) |
n.s. = non-significative; * 33.3% of nDNA and 29.4% of mtDNA patients presented a normal Electromyography (EMG) while 48.2% and 47.1% showed neuropathic features; M, male; F, female; CPK, creatine phosphate kinase; RRF, ragged red; SDH, succinate dehydrogenase; COX, cytochrome c oxidase.