ACAD8 and metabolic disease: Isobutyryl-CoA dehydrogenase (IBD) deficiency (IBDD, OMIM#611283) is a rare autosomal recessive metabolic disorder involving defects in valine metabolism [1], which is caused by biallelic variants in ACAD8 (acyl-CoA dehydrogenase family member 8; OMIM*604773) on chromosome 11q25 [2].