BACKGROUND: Kawasaki disease (KD) is a self limited vasculitis in which host genetics plays a prominent role. To further the understanding of the role of host genetics in KD, a three-stage genetic study was conducted that began with a family linkage study and ultimately involved more than 3000 individuals to identify new genetic contributions to KD susceptibility. METHODS AND RESULTS: A 26-family linkage study followed by fine mapping was performed in a cohort of 1284 KD subjects and their family members (total 3248 individuals). Suggestive evidence of disease linkage (logarithm of odds (LOD) ≥3.0, p<1.00×10(-4)) was found for five genomic locations (Chr 3q, 4q, 10p, 13q, 21q). Two of these loci (Chr 4q and Chr 13q) overlapped with validated findings from a recent KD genome-wide association study. Fine mapping analysis revealed three single nucleotide polymorphisms (SNPs) in ATP-binding cassette, subfamily C, member 4 (ABCC4) underlying the Chr 13q linkage peak showing evidence of association to KD (lowest p=8.82×10(-5); combined OR 2.00, 95% CI 1.41 to 2.83). ABCC4 is a multifunctional cyclic nucleotide transporter that stimulates the migratory capacity of dendritic cells. It is also a mediator of prostaglandin efflux from human cells and is inhibited by non-steroidal anti-inflammatory medications such as aspirin. CONCLUSION: These genetic data suggest that ABCC4 could play a fundamental role in KD pathogenesis with effects on immune activation and vascular response to injury.