The mutations in TBX4 related to PAH in children are mainly concentrated in key T-box domains, often leading to impaired amino acid displacements or premature truncation of mutational transcripts (Arora et al., 2012; Kerstjens-Frederikse et al., 2013; Levy et al., 2016). The gene discussed is TBX4; the disease is pulmonary arterial hypertension.