Table 2.
Comparison of characteristics between mitochondrial myopathy (MM) and non-MM phenotypes.
| Characteristics | MM | Non-MM | p value |
|---|---|---|---|
| Male | 7/14 (50.00%) | 7/17 (41.18%) | 0.725 |
| Age at onset (years) | 10.5 [8, 26.25] | 6 [0.625, 9.5] | 0.007** |
| Number of involved systems | 1 [1, 1] | 4 [2, 5] | < 0.001*** |
| De novo variants | 7/7 (100.00%) | 11/13 (84.62%) | 0.521 |
| Truncating variants | 8/17 (47.06%) | 2/17 (11.76%) | 0.057 |
| Missense variants | 8/17 (47.06%) | 12/17 (70.59%) | 0.296 |
| Glycine residue variantsa | 7/17 (41.18%) | 4/17 (23.53%) | 0.465 |
| Transmembrane domain variants | 8/17 (47.06%) | 9/17 (52.94%) | 1.000 |
| Nucleotide substitution variants | 16/17 (94.12%) | 13/17 (76.47%) | 0.335 |
| Muscle-restricted variants | 15/17 (88.24%) | 1/16 (6.25%) | < 0.001*** |
| Muscle heteroplasmy level | 80 [66.5, 91] | 88 [64.5, 95] | 0.615 |
| Muscle heteroplasmy level > 85% | 5/17 (29.41%) | 8/13 (61.54%) | 0.138 |
| Isolated CIII deficiency | 14/17 (82.35%) | 11/16 (68.75%) | 0.438 |
aGlycine residue variants were defined as variants affecting at least one glycine residue. Data are presented as median [25th percentile, 75th percentile] or n/N (%), as appropriate. Continuous variables were compared using the Mann–Whitney U test, and categorical variables were compared using Fisher’s exact test. Asterisks indicate statistical significance (*p < 0.05, **p < 0.01, ***p < 0.001).
MM, mitochondrial myopathy; CIII, complex III.