NDUFS6 related Leigh syndrome: a case report and review of the literature

The genetic causes of Leigh syndrome are heterogeneous, with a poor genotype–phenotype correlation. To date, more than 50 nuclear genescause nuclear gene-encoded Leigh syndrome. NDUFS6encodes a 13 kiloDaltonssubunit, which is part of the peripheral arm of complex I and is localized in the iron-sulfur fraction. Only a few patients were reported with proven NDUFS6pathogenic variants and all presented with severe neonatal lactic acidemia and complex I deficiency, leading to death in the first days of life. Here, we present a patient harboring two NDUFS6variants with a phenotype compatible with Leigh syndrome. Although most of previous reports suggested that NDUFS6pathogenic variants invariably lead to early neonatal death, this report shows that the clinical spectrum could be larger. We found a severe decrease of NDUFS6protein level in patient’s fibroblasts associated with a complex I assembly defect in patient’s muscle and fibroblasts. These data confirm the importance of NDUFS6and the Zn-finger domain for a correct assembly of complex I.