Some hotspot variants resulting in the defect of enzymes have been identified in patients with IMEs, such as ACADS variants c.511C > T and c.625G > A for short chain acyl-CoA dehydrogenase deficiency (SCADD; MIM# 201470) (Tonin et al., 2016; Nochi et al., 2017), PAH variant c.728C > A for phenylketonuria (PKU; MIM# 261600) (Liu et al., 2017), and so on. Here, ACADS is linked to pulmonary arterial hypertension.