Ethylmalonic acid (EMA) is the main metabolite excreted in the urine of patients suffering of two distinct inborn errors of metabolism with muscular and neurological implications, namely ethylmalonic encephalopathy (EE; OMIM # 602473) [1,2], and short-chain acyl-CoA dehydrogenase (SCAD; EC 1.3.8.1) deficiency (SCADD; OMIM # 201470) [3]. Here, ACADS is linked to short chain acyl-CoA dehydrogenase deficiency.