False-positive screening results due to maternal IMDs are reported for PKU (PAH, MIM *612349, #261600), 3-methylcrotonylglycinuria (MCCC1, MIM *609010, #210200; MCCC2, MIM *609014, #210210), primary carnitine deficiency (SLC22A5, MIM *603377, #212140), medium-chain acyl-CoA dehydrogenase deficiency (MCAD) (ACADM, MIM *607008, #201450), and glutaric acidemia type 1 (GDCH, MIM *606601, #231670) [7,11]. This evidence concerns the gene MCCC2 and medium chain acyl-CoA dehydrogenase deficiency.