ABSTRACTS BJD British Journal of Dermatology Psoriasis: from Gene to Clinic 6th International Congress, 2011 Oral presentations FC-1 Detection of copy number variants at new psoriasis loci identified by genome-wide association studies M. Apel, S. Uebe, A.B. Ekici, F. Behrens,* B. Bo ¨hm,* H. Traupe, R. Mo ¨ssner,à H. Burkhardt,* A. Reis and U. Hu ¨ffmeier Institute of Human Genetics, University of Erlangen-Nuremberg, Erlangen, Germany; *Division of Rheumatology, Department of Internal Medicine II, Johann Wolfgang Goethe University, Frankfurt/Main, Germany;  Depart- ment of Dermatology, Mu ¨nster, Germany and àDepartment of Dermatology, Go¨ttingen,Germany In the last few years, several genome-wide association studies revealed a considerable number of new genetic susceptibility loci for psoriasis (Ps) and psoriatic arthritis (PsA). As causative variants can either be single nucleotide polymorphisms (SNPs) or copy number polymorphisms (CNPs), we tested whether CNPs can be identified at those susceptibility loci. Using the Birdsuite algorithm package, microarray data (Affymetrix 6.0) of 600 PsA patients were analysed regarding possible CNPs at Ps/ PsA susceptibility loci. Apart from the known deletion at the LCE3 gene cluster, we identified a common deletion in the HLA-C gene. Because sequences at this locus are highly similar to those of the HLA-B gene, generation of an alternative genetic validation method was not possible. Therefore we assume that this CNP might be an artifact. At 10 further Ps susceptibility loci, we identified (very) rare deletions and duplications. In order to validate copy number states at the first five loci, we established MLPA as an alternative method. While no copy number change was confirmed at three loci, deletions in in- trons of CSMD1 and RYR2 were successfully validated in one and two individual(s), respectively. Validation of copy number states at the further five susceptibility loci are ongoing. Our study results suggest that common CNPs at Ps susceptibility loci are not susceptibility factors in German PsA patients. FC-2 Replication of 18 psoriasis genetic associations in Caucasians R.P. Nair, E. Ellinghaus,* L.C. Tsoi, T. Esko,  P.E. Stuart, T. Tejasvi, V. Chandran,à F. Pellett,à L. Peddle,§ M. Weichenthal,* S. Weidinger,* U. Mrowietz,* T. Balschun,* A. Metspalu,  J.J. Voorhees, G.R. Abecasis, P. Rahman,§ D.D. Gladman,à A. Franke* and J.T. Elder University of Michigan, Ann Arbor, MI, U.S.A.; *University of Kiel, Kiel, Germany;  University of Tartu, Tartu, Estonia; àUniversity of Toronto, Toronto, ON, Canada and §Memorial University, St John’s, NF, Canada Psoriasis is a common, immune-mediated disease of genetic and environmental aetiology. Recent genetic association studies identified 25 psoriasis susceptibility loci of genome-wide signif- icance (P <5 · 10 )8 ). Five of these associations were observed in Caucasian and Chinese populations, 15 in Caucasians only, and 5 in Chinese only. Multiple susceptibility loci have been found for other autoimmune diseases such as rheumatoid arthri- tis, type 1 diabetes, Crohn disease, lupus and ulcerative colitis. More than one of these diseases is often found in the same per- son or family, and many of the identified susceptibility loci overlap. With the goal of understanding the overlap between these autoimmune diseases and their underlying genetics, a group of autoimmune genetic disease researchers collaborated to design a custom high-throughput single nucleotide polymor- phism (SNP) genotyping array, the Immunochip, that would interrogate confirmed and potential susceptibility loci identified in previous genome-wide association studies (GWAS). The Im- munochip contains 196 524 SNP markers representing 292 po- tential loci for 13 autoimmune diseases. These SNPs were selected to allow association testing as well as high-density fine mapping, and included variants identified from the 1000 Ge- nomes sequencing project. Markers from 23 of the 25 known psoriasis susceptibility loci were present on the Immunochip; b- defensin CNV and the gene desert near rs6809854 (chr 3p24) were not represented. We assembled a GWAS-independent cohort of 4057 psoriasis cases and 7439 controls of European Caucasian ancestry collected in the U.S.A., Canada, Germany and Estonia, and genotyped on the Immunochip. After stringent quality controls for marker quality (removal of SNP call rate < 95%, minor allele frequency <0Æ005, Hardy–Weinberg P >1 · 10 )7 ) and samples (removal of population outliers based on principal component analysis, samples with genotype rate < 98%, related individuals) 134 876 markers and 10 874 samples (3736 cases and 7138 controls) were available for asso- ciation analysis by a variance component approach. Of the 23 loci tested, 10 (HLA-C, IL12B, TNIP1, TNFAIP3, TRAF3IP2, FBXL19, NOS2, IF1H1, TYK2, LCE3B/LCE3C) yielded genome-wide signifi- cant association (P <5 · 10 )8 ), and 8 (IL13/IL4, IL23A, IL23R/ STAT2, NFKBIA, IL28RA, REL, ERAP1, RNF114) showed confirma- tory evidence of association (P < 10 )4 ). All of these 18 loci were previously reported to be associated in Caucasians, and five were also associated in Chinese. The remaining five loci (PTTG1, CSMD1, GJB2, SERPINB8, ZNF816A) with no evidence of associa- tion (P < 10 )4 ) had previously reported significant association only in the Chinese population. These results replicate 18 psori- asis susceptibility loci and suggest that five loci previously reported in the Chinese population may not be disease-associ- ated in Caucasians. Ó 2011 The Authors BJD Ó 2011 British Association of Dermatologists 2011 e1