Asthma susceptibility loci determined by genome-wide association studies explain only a fraction of asthma's hereditability. Pathway analysis has emerged as a next step toward mining hidden genetic factors in complex diseases. A recent study investigating the association between polymorphisms in Toll-like receptor signaling pathways and asthma revealed that 2 members of the mitogen-activated protein kinase (MAPK) pathway (MAP kinase kinase 3 and extracellular signal-regulated kinase 2 [ERK2]) showed strong association with the disease