Beta-ketothiolase deficiency (BKTD, OMIM #203750) is an autosomal recessive disorder caused by a defect in mitochondrial acetoacetyl-CoA thiolase (T2, EC 2.3.1.9) that affects both isoleucine catabolism and ketolysis [1–3]. This evidence concerns the gene ACAT1 and beta-ketothiolase deficiency.