Table 1.
Correlation of SMN2 copy number and disease severity
| # SMA patients | SMA types | Correlation of SMN2 copy number and disease severity | Reference |
|---|---|---|---|
| Strong correlation | |||
| 142 | I/III | Good correlation | Mailman et al.61 |
| 50 | I/II/III | Good correlation | Kesari et al.62 |
| 87 | II | Good correlation to HFMS in SMA type II | Tiziano et al.63 |
| 143 | I/II/III | 1–2 SMN2 copies predict early disease onset and poor survival | Taylor et al.64 |
| 26 | I | Correlation with risk of death or permanent invasive ventilatory support | Kolb et al.47 |
| 3 | asymptomatic | Five SMN2 copies are protective in case of homozygous SMN1 deletion | Prior et al.25 |
| Modest correlation | |||
| 115 | III/IV | Strong correlation of 1–2 copies with severe phenotype and four or more copies with mild phenotype, strong overlap in cases of three copies | Wirth et al.65 |
| NA | I/II/III | Modifying role in MUNE and CMAP and overall functional status | Swoboda et al.50 |
| 36 | I/II/III | Modest correlation | Czech et al.29 |
| 42 | I/II/III | Correlation exists, but better predictor when combined with NAIP mutation analysis | Watihayati et al.66 |
| 375 | I/II/III | Correlation exists, but great overlap between groups | Feldkotter et al.67 |
| 27 | I/II/III | Correlation exists, but great overlap between groups | Harada et al.68 |
| 51 | I/II/III | Correlation exists, but great overlap between groups | Tiziano et al.31 |
| 144 | I/II/III | Correlation exists, but great overlap between groups | Medrano et al.69 |
| 3459 | I/II/III/IV | Correlation exists, but great overlap between groups, especially in cases of 2–3 copies | Calucho et al.22 |
| 45 | I/II/III | Correlation exists, but siblings with different phenotypes show identical SMN2 copy numbers | Cusco et al.23 |
| Poor correlation | |||
| 48 | I/II/III | No correlation | Vezain et al.32 |
| 45 | III | No correlation | Tiziano et al.28 |
| 61 | II/III | Four SMN2 copies in a family member with SMA type III and unaffected sibling and five SMN2 copies in unaffected family member | Zheleznyakova et al.24 |
| 108 | I/II/III | SMA type I patients with four or five copies exist | Crawford et al.26 |
CMAP, compound muscle action potential; HFMS, Hammersmith Functional Motor Scale; MUNE, motor unit number estimation; NAIP, neuronal apoptosis inhibitory protein; SMA, spinal muscular atrophy; SMN, survival motor neuron.