1. ¹Centre National de Génotypage, Evry, France
2. ²INSERM, U535, Villejuif, France
3. ³Université Paris-Sud, IFR69, Villejuif, France
4. ⁴Généthon, Evry, France
5. ⁵Department of Human Genetics, University of California, Los Angeles, California, USA

Correspondence: Fabienne Lesueur, FRE2939, CNRS, Institut de Cancérologie Gustave Roussy, Université Paris-Sud, 94805 Villejuif, France. E-mail: flesueur@igr.fr; Judith Fischer, Centre Nationale de Génotypage, 2 rue Gaston Crémieux, 91057 Evry Cedex, France. E-mail: fischer@cng.fr

Received 3 August 2006; Revised 30 November 2006; Accepted 7 December 2006; Published online 8 March 2007.

Abstract

Plaque psoriasis is a chronic inflammatory disorder of the skin. It is inherited as a multifactorial trait, with a strong genetic component. Linkage studies have identified a large number of disease loci, but very few could be replicated in independent family sets. In this study, we present the results of a genome-wide scan carried out in 14 French extended families. Candidate regions were then tested in a second set of 32 families. Analysis of the pooled samples confirmed linkage to chromosomes 6p21 (Z_MLB score=3.5, P=0.0002) and 20p13 (Z_MLB score=2.9, P=0.002), although there was little contribution of the second family set to the 20p13 linkage signal. Moreover, we identified four additional loci potentially linked to psoriasis. The major histocompatibility complex region on 6p21 is a major susceptibility locus, referred to as PSORS1, which has been found in most of the studies published to date. The 20p13 locus segregates independently of PSORS1 in psoriasis families. It has previously been thought to be involved in the predisposition to psoriasis and other inflammatory disorders such as atopic dermatitis (AD) and asthma. Although psoriasis and AD rarely occur together, this reinforces the hypothesis that psoriasis is influenced by genes with general effects on inflammation and immunity.