TBX4 and pulmonary arterial hypertension: Recently, we also reported variants in CTNNB1 and TBX4, encoding crucial members of the Wnt and FGF signaling, in a newborn with abnormal lung growth, PAH, severe microcephaly, and spasticity, suggesting that mutations in these genes could act synergistically resulting in a lethal respiratory failure during the neonatal period [38].