A de novo novel variant in the MT-TD gene is associated with prominent extra-neurologic manifestations.

Abstract

Defects in the mitochondrial tRNA genes cause a group of highly clinically and genetically heterogeneous disorders, which poses a challenge for clinical identification and genetic diagnosis. Here, we present a pre-school boy with a novel MT-TD variant m.7560T>C at the heteroplasmy level of 76.53% in blood, 93.34% in urine sediments, and absent in the healthy mother's blood and urine. Besides convulsions, brain magnetic resonance imaging abnormalities and high plasma lactate, the boy presented with the prominent extra-neurologic phenotype including steroid-resistant nephrotic syndrome associated with focal segmental glomerulosclerosis characterized by abnormal mitochondria in podocytes, cortical blindness, and pancreatitis. To our knowledge, this is the unique case with MT-TD m.7560T>C-related multi-organ impairments, which expands the phenotypic and mutational spectrum of primary mitochondrial diseases.