Our verdict is Uncertain significance. The variant received 5 ACMG points: 5P and 0B. PS1PP3
The NM_001377299.1(NDUFS2):c.268_270delGCAinsACC(p.Ala90Thr) variant causes a missense change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. It is difficult to determine the true allele frequency of this variant because it is of type MNV, and the frequency of such variant types in population databases may be underestimated and unreliable. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar. Another nucleotide change resulting in the same amino acid substitution has been previously reported as Likely pathogenic in ClinVar.
NDUFS2 (HGNC:7708): (NADH:ubiquinone oxidoreductase core subunit S2) The protein encoded by this gene is a core subunit of the mitochondrial membrane respiratory chain NADH dehydrogenase (complex I). Mammalian mitochondrial complex I is composed of at least 43 different subunits, 7 of which are encoded by the mitochondrial genome, and the rest are the products of nuclear genes. The iron-sulfur protein fraction of complex I is made up of 7 subunits, including this gene product. Complex I catalyzes the NADH oxidation with concomitant ubiquinone reduction and proton ejection out of the mitochondria. Mutations in this gene are associated with mitochondrial complex I deficiency. Alternatively spliced transcript variants encoding different isoforms have been found for this gene.[provided by RefSeq, Oct 2009]
NDUFS2 Gene-Disease associations (from GenCC):
Leigh syndrome
Inheritance: AR Classification: DEFINITIVE Submitted by: ClinGen
mitochondrial complex I deficiency, nuclear type 6