TBX4 and idiopathic pulmonary arterial hypertension: The detrimental variants in TBX4 account for about 2.1%–25% of childhood-onset PAH, and predominantly occur in IPAH cases (Kerstjens-Frederikse et al., 2013; Levy et al., 2016; Zhu et al., 2018a; Eyries et al., 2019; Galambos et al., 2019; Zhu et al., 2019; Haarman et al., 2020; Abman et al., 2022).