We compared the survival of SURF1 deficiency to 56 patients with LRPPRC deficiency [8] and 63 patients with nuclear-encoded complex I-deficient LS/“Leigh- like” disease [9] Median survival length was longer in patients with SURF1 deficiency (median 5.4, 25th centile 3.0, 75th centile 10 years) than in patients with LRPPRC deficiency (median 1.8, 25th centile 1.0, 75th centile 4 years), and nuclear-encoded complex I-deficient LS (median 1.6, 25th centile 1.0, 75th centile 10 years) (p < 0.001 for difference across groups; logrank test). The gene discussed is SURF1; the disease is hyperinsulinemic hypoglycemia, familial, 4.