Background: Scleroderma renal crisis (SRC) is a severe complication of SSc. Most SSc cases demonstrate a disease-specific ANA, for example anti-RNA polymerase III, anti-fibrillarin (AFA), anti-topisomerase-1 (ATA) or ACA antibody. Previous studies have confirmed antiRNA polymerase III as a powerful serological predictor of SRC. We developed an innovative approach to identify genetic susceptibility loci for SRC using an anti-RNA polymerase IIIþ cohort of SSc cases distinguished by occurrence of SRC. Methods: First we analysed SRC in a well characterized group of SSc cases followed at our centre (n1⁄4 415). Informed by this, 50 patients with confirmed SRC and anti-RNA polymerase IIIþ and another 50 SSc anti-RNA polymerase IIIþ that had never developed SRC were identified from our larger SSc cohort. These cases, all with Northern European ancestry, were genotyped across approximately one million SNPs using the Illumina Human Omni-express bead array chip. All data underwent quality control checks for Hardy-Weinberg equilibrium and genotyping rate in PLINK (HWE; P<0.001 and a genotyping rate of >90%). After filtering of SNPs, a logistic regression was performed in PLINK comparing patients with or without SRC to determine the genetic signature difference between these two groups of patients. Results: Initial analysis confirmed a strong association between antiRNA polymerase III and SRC with 30% anti-RNA polymerase IIIþ SSc developing SRC compared with 7% AFA, 4% ATA and 1% ACA (P<0.001). Moreover, in anti-RNA polymerase IIIþcases almost all SRC occurred within 18 months of disease onset, and SRC after 5 years of follow up was very rare. Thus we could define a group with SRC and another at very low risk. This dichotomy formed the basis of our genetic analysis comparing anti-RNA polymerase IIIþ patients with SRC history (Group A) to the control group, who had been followed for >60 months without SRC (Group B). We performed genome-wide association study analysis on these two groups. Quality control checks removed 2309 SNPs for missingness (GENO >0.1) and 77 122 failed minor allele frequency (MAF) filters (MAF <0.01). In total 641 489 SNPs were analysed. The logistic regression analysis identified a number of SRC associated SNPs within genes and gene regions. Top associations were found in the complement region (P1⁄4 1.66 10 ), and in other genes including EPHA5 (P1⁄41.87 10 ), GRIA3 (P1⁄42.16 10 ), HECW2 (P1⁄4 2.71 10 ) and CTNND2 (P1⁄42.92 10 ). Conclusion: We present a novel study using extreme phenotypes of anti-RNA polymerase IIIþ SSc to identify genetic association of SRC in cases that are serologically and clinically otherwise homogeneous. We identified genes including catenin cadherin-associated protein delta 2 (CTNND2), which is known to regulate adhesion molecules relevant to fibrosis. Genes identified from this analysis may have general relevance to SSc vasculopathy or other forms of hypertensive thrombotic microangiopathy. Additional functional and genetic replication studies are needed. Disclosure statement: The authors have declared no conflicts of interest.