MADD is caused by pathogenic variants in the ETFA (MIM *608053; glutaric acidemia IIA), ETFB (MIM *130410; glutaric acidemia IIB), and ETFDH (MIM *231675; glutaric acidemia IIC) genes, which encode the alpha and beta subunits of the electron transfer flavoprotein (ETF) and ETF-coenzyme Q oxidoreductase [3,4]. Here, ETFB is linked to Elevated circulating glutaric acid concentration.