Molecular and cellular pathology of very-long-chain acyl-CoA dehydrogenase deficiency

► VLCAD deficiency (VLCADD) is now diagnosed in the US through newborn screening. ► Numerous NBS variant patterns can represent mild disease or heterozygous carriers. ► 13 patient samples suspected of VLCADD were retrospectively investigated. ► Prokaryotic expression studies were performed for nine missense ACADVL mutations. ► Functional investigation of equivocal NBS or clinical testing is crucial to diagnose disease.