Summary To gain further insight into the genetic architecture of psoriasis, we conducted a meta-analysis of three genome-wide association studies (GWAS) and two independent datasets genotyped on the Immunochip, involving 10,588 cases and 22,806 controls in total. We identified 15 new disease susceptibility regions, increasing the number of psoriasis-associated loci to 36 for Caucasians. Conditional analyses identified five independent signals within previously known loci. The newly identified shared disease regions encompassed a number of genes whose products regulate T-cell function (e.g. RUNX3, TAGAP and STAT3). The new psoriasis-specific regions were notable for candidate genes whose products are involved in innate host defense, encoding proteins with roles in interferon-mediated antiviral responses (DDX58), macrophage activation (ZC3H12C), and NF-κB signaling (CARD14 and CARM1). These results portend a better understanding of shared and distinctive genetic determinants of immune-mediated inflammatory disorders and emphasize the importance of the skin in innate and acquired host defense.

To identify new susceptibility loci for psoriasis, we undertook a genome-wide association study of 594,224 SNPs in 2,622 individuals with psoriasis and 5,667 controls. We identified associations at eight previously unreported genomic loci. Seven loci harbored genes with recognized immune functions (IL28RA, REL, IFIH1, ERAP1, TRAF3IP2, NFKBIA and TYK2). These associations were replicated in 9,079 European samples (six loci with a combined P < 5 × 10⁻⁸ and two loci with a combined P < 5 × 10⁻⁷). We also report compelling evidence for an interaction between the HLA-C and ERAP1 loci (combined P = 6.95 × 10⁻⁶). ERAP1 plays an important role in MHC class I peptide processing. ERAP1 variants only influenced psoriasis susceptibility in individuals carrying the HLA-C risk allele. Our findings implicate pathways that integrate epidermal barrier dysfunction with innate and adaptive immune dysregulation in psoriasis pathogenesis

Prominent skin involvement is a defining characteristic of autoinflammatory disorders caused by abnormal IL-1 signaling. However, the pathways and cell types that drive cutaneous autoinflammatory features remain poorly understood. We sought to address this issue by investigating the pathogenesis of pustular psoriasis, a model of autoinflammatory disorders with predominant cutaneous manifestations. We specifically characterized the impact of mutations affecting AP1S3, a disease gene previously identified by our group and validated here in a newly ascertained patient resource. We first showed that AP1S3 expression is distinctively elevated in keratinocytes. Because AP1S3 encodes a protein implicated in autophagosome formation, we next investigated the effects of gene silencing on this pathway. We found that AP1S3 knockout disrupts keratinocyte autophagy, causing abnormal accumulation of p62, an adaptor protein mediating NF-κB activation. We showed that as a consequence, AP1S3-deficient cells up-regulate IL-1 signaling and overexpress IL-36α, a cytokine that is emerging as an important mediator of skin inflammation. These abnormal immune profiles were recapitulated by pharmacological inhibition of autophagy and verified in patient keratinocytes, where they were reversed by IL-36 blockade. These findings show that keratinocytes play a key role in skin autoinflammation and identify autophagy modulation of IL-36 signaling as a therapeutic target.

The association between psoriasis and risk of major cardiovascular (CV) events (myocardial infarction, acute coronary syndrome, unstable angina, and stroke) is unclear. A cohort study with 48,523 patients with psoriasis and 208,187 controls was conducted. During a median follow-up of 5.2 years, 1,257 patients with psoriasis (2.59%) had a major CV event, compared with 4,784 controls (2.30%). In the multivariable analysis, inflammatory arthritis hazard ratio (HR) 1.36 (1.18-1.58), diabetes HR 1.18 (1.06-1.31), chronic kidney disease HR 1.18 (1.07-1.31), hypertension HR 1.37 (1.29-1.45), transient ischemic attack HR 2.74 (2.41-3.12), atrial fibrillation HR 1.54 (1.36-1.73), valvular heart disease HR 1.23 (1.05-1.44), thromboembolism 1.32 (1.17-1.49), congestive heart failure HR 1.57 (1.39-1.78), depression HR 1.16 (1.01-1.34), current smoker HR 2.18 (2.03-2.33), age (year) HR 1.07 (1.07-1.07), and male gender HR 1.83 (1.69-1.98) were statistically significant for the risk of major CV events. The age- and gender-adjusted HRs of a major CV event for psoriasis were 1.10 (1.04-1.17) and for severe psoriasis 1.40 (1.07-1.84), whereas the fully adjusted HRs were attenuated to 1.02 (0.95-1.08) and 1.28 (0.96-1.69). In conclusion, neither psoriasis nor severe psoriasis were associated with the short-to-medium term (over 3-5 years) risk of major CV events after adjusting for known cardiovascular disease risk factors.