Cardiac transplant outcomes in a pediatric patient with novel homozygous variants in TOP3Α causing mitochondrial dysfunction.

Pathogenic variants TOP3A gene have been recently described to cause a multisystem disorder associated with mitochondrial dysfunction in adults (Nicholls et al., 2018 [1]) and with a Bloom syndrome-like disorder in children (Martin et al., 2018 [2]). We present the case of an 11-year-old male with homozygosity for a novel variant in TOP3A with myopathy, ataxia, and atrioventricular conduction defect similar to the adult cases described in the literature. He developed dilated cardiomyopathy and presented in acute decompensated heart failure requiring left ventricular assist device support as a bridge to heart transplantation. Clinical and laboratory features showed mitochondrial dysfunction confirming pathogenicity of the TOP3A variants. However, unlike the other pediatric cases of TOP3A related disease reported so far, the features of Bloom syndrome were not evident in this patient.