AIM: To study the concordance of psoriasis in a population-based twin sample. METHODS: Data on psoriasis in 10,725 twin pairs, 20-71 years of age, from the Danish Twin Registry was collected via a questionnaire survey. The concordance and heritability of psoriasis were estimated. RESULTS: In total, 4.1% of the men and 4.2% of the women had a lifetime history of psoriasis. The probandwise concordance for psoriasis was larger in monozygotic than in dizygotic twins, 0.33 vs. 0.17. Genetic factors explained 68% (60-75%) of the variation in the susceptibility to psoriasis, whereas the rest of the variation was explained by non-shared environmental factors. CONCLUSION: The results confirm that psoriasis is a complex multifactorial disease controlled by both exogenous and endogenous factors. This article is protected by copyright. All rights reserved.
British Journal of Dermatology, 2013, Vol 169, Issue 2, p. 412-416