MTO1-related mitochondrial disease (Combined Oxidative Phosphorylation Deficiency type 10, COXPD10; OMIM #614702) is a rare autosomal recessive disorder caused by biallelic variants in the nuclear MTO1 gene, which encodes an enzyme that modifies mitochondrial transfer RNA so that mitochondria can synthesise their proteins correctly. It typically presents in infancy with lactic acidosis and hypertrophic cardiomyopathy and, in longer-surviving children, evolves into a multisystem disorder with intellectual disability, epilepsy and optic neuropathy, a pattern termed ONCE syndrome (Optic Neuropathy, Cardiomyopathy, Encephalopathy with lactic acidosis and combined OXPHOS deficiency). We report a 12-year-old girl, the third child of consanguineous parents, with global psychomotor delay and persistent mild hyperlactataemia from infancy. Brain imaging showed symmetric T2 hyperintensity in both dentate nuclei with a cerebral lactate peak on MR spectroscopy. Whole-exome sequencing identified a homozygous MTO1 missense variant (c.1402G>A; p.Ala468Thr), consistent with the molecular diagnosis of COXPD10, with both parents heterozygous carriers; an incidental heterozygous FBN1 variant (p.Arg609Cys) was classified as a variant of uncertain significance and judged unrelated. She developed myoclonic epilepsy at age 11, managed with lamotrigine, while echocardiography and ophthalmological examination remained normal at age 12. We review the molecular pathogenesis, genotype-phenotype correlations and treatment options for MTO1 deficiency, focusing on dichloroacetate as adjunctive therapy for lactic acidosis and cardiomyopathy, and place the case alongside the 2025 FDA approval of elamipretide for Barth syndrome and emerging gene-therapy approaches. Early genetic diagnosis and structured cardiac and ophthalmological surveillance are essential; prospective studies of dichloroacetate are needed.

Circumcision, a commonly performed procedure in the neonatal period, is the surgical removal of the prepuce. The complications of male circumcision are common, but post circumcision penile shaft fibromas are rare and there is paucity of cases reported in literature worldwide. A 4-year-old boy presented with distal penile shaft swelling that encircled the penis along the circumcision scar that was noticed few months after circumcision. He had no history of trauma apart from the circumcision he had at the neonatal period and a clinical diagnosis of penile shaft fibroma was made. The swelling was excised under general anaesthesia and sent for histopathological confirmation. This case is reported to draw clinicians’ attention to this rare post circumcision complication.

Sinus node disease (SND) is a leading indication for permanent pacemaker implantation and is classically attributed to age-related degenerative changes. Nevertheless, functional conditions may result in similar clinical and electrocardiographic presentations, particularly in atypical cases. Extra-cardiac thoracic masses causing cardiac compression are rare and often underrecognized. We report the case of a patient presenting with a tachycardia-bradycardia syndrome initially suggestive of SND, in whom a comprehensive etiological evaluation revealed an esophageal tumor causing significant left atrial compression. This unusual presentation highlights the importance of considering extracardiac structural abnormalities in the differential diagnosis of apparent sinus node dysfunction.