Recently, Karolak et al. analyzed the molecular change of lethal lung developmental disorders (LLDDs), including alveolar capillary dysplasia with misalignment of pulmonary veins (ACDMPV), acinar dysplasia (AcDys), congenital alveolar dysplasia (CAD), and primary pulmonary hypoplasia, which involve the loss-of-function of FOXF1, TBX4, or FGF10. Through transcriptome analysis, they showed that TMEM100 is one of the six significant deregulated genes in the lungs of patients with either TBX4 or FGF10 variants. The gene discussed is TMEM100; the disease is alveolar capillary dysplasia with misalignment of pulmonary veins.