Loss-of-function variants in NIPBL cause Cornelia de Lange syndrome; missense variants in ACTG1 lead to Baraitser-Winter syndrome; missense variants in ATP1A3 underlie Snijders Blok-Campeau syndrome; and loss-of-function variants in TCF4 result in Pitt-Hopkins syndrome. The gene discussed is NIPBL; the disease is Pitt-Hopkins syndrome.