The mtDNA copy number showed the opposite direction of effect and was significantly higher in SOD1 ALS patients (175.02 ± 56.83) with respect to control subjects (127.75 ± 56.27; p = 0.04, 95% CI − 93.49 to − 1.04), while it showed a non-significant increase in sporadic ALS patients (145.33 ± 56.28; p = 0.91, − 50.41 to 15.23) compared to controls, and was similar between controls and C9orf72 ALS patients (121.66 ± 56.85; p = 1.00, 95% CI − 41.58 to 53.75) (Fig. 5b). The gene discussed is SOD1; the disease is amyotrophic lateral sclerosis.