Despite substantial progress in understanding the NF-kappaB signaling pathw
ay, the connections between this pathway and human disease are only now bei
ng elucidated. Genes that function within or upstream of the NF-kappaB path
way have been found to cause four distinct disorders and two allelic condit
ions. Investigation of these genes and disorders has brought significant in
sight into the role of NF-kappaB in various aspects of physiological develo
pment.