HIBCH and 3-hydroxyisobutyryl-CoA hydrolase deficiency: To date, just 31 HIBCH gene mutations have been reported, with 34 patients on a broad phenotypic spectrum ranging from early death (Brown et al., 1982; D’Gama et al., 2020) to just movement disorder with survival into adulthood, although the estimated incidence of HIBCH deficiency was 1 in ∼130,000 individuals (Stiles et al., 2015).