The NM_000018.4(ACADVL): c.779C>T (p.Thr260Met) variant is a missense variant predicted to cause substitution of threonine by methionine at amino acid 260. This variant has been detected in individuals with very long chain acyl CoA dehydrogenase (VLCAD) deficiency and VLCAD enzyme activity of less than 20%, which is highly specific for VLCAD deficiency (PP4_Moderate, PMID: 8845838, 17374501, 32518924). This variant was found homozygous in two individuals with VLCAD deficiency (PM3, 1.0 point, PMIDs: 9327992, 32518924). Two enzyme activity assays in Cos-7 cells and E.coli showed residual enzyme activity between 3-5% of wildtype indicating that this variant impacts protein function (PMIDs: indicating that this variant impacts protein function (PMID: 9973285, 9973285; PS3_supporting). The highest population minor allele frequency in gnomAD v2.1.1 is 0.00002 in the non-Finnish European population, which is lower than the ClinGen ACADVL Variant Curation Expert Panel threshold (<0.001) for PM2_Supporting, meeting this criterion (PM2_Supporting). The computational predictor REVEL gives a score of 0.875, which is above the threshold of 0.75, evidence that correlates with impact to ACADVL function (PP3). In summary, this variant meets the criteria to be classified as likely pathogenic for autosomal recessive VLCAD deficiency based on the ACMG/AMP criteria applied, as specified by the ClinGen ACADVL Variant Curation Expert Panel: PM2_Supporting, PM3_moderate, PP3, PP4_Moderate, PS3_supporting (ACADVL VCEP specifications version 1; approved November 9, 2021).