1 Variants in CALCRL, EPHB4, PIEZO1, and ITGA9 are associated with prenatal CCLA and GLD and precipitate nonimmune hydrops and chylothorax.19–22 LAs are often present as part of RASopathy syndromes with variants in the genes PTPN11, RAF1, NRAS, KRAS, HRAS, RASA1, RIT1, SOS1, and SOS2. LAs are also found as part of complex syndromes due to chromosomal abnormalities or variants in PTEN, TSC1, TSC2, and AKT1. The gene discussed is RASA1; the disease is Chylothorax.