By Sanger sequencing we screened MTO1 in a cohort of mitochondrial defective patients with cardiomyopathy, and found that Pt1 was compound heterozygous for the previously described c.1402G>A/p.Ala428Thr mutation and for a novel missense substitution (c.1430G>A/p.Arg477His), whereas siblings Pt2 and Pt3 harbored a homozygous c.1232C>T/p.Thr411Ile change (Fig. 1A). The gene discussed is MTO1; the disease is cardiomyopathy.