HIBCH and 3-hydroxyisobutyryl-CoA hydrolase deficiency: HIBCH mutations were first identified to cause HIBCH deficiency (HIBCHD, OMIM #250620) in 2007 (Loupatty et al., 2007), and it was reported that it could lead to Leigh/Leigh-like disease due to secondary oxidative phosphorylation (OXPHOS) defects (Figure 1B) (Ferdinandusse et al., 2013; Yamada et al., 2014; Soler-Alfonso et al., 2015; Stiles et al., 2015).